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EXPERIMENTAL ENQUIRY UPON THE AFFERENT TRACTS OF THE CENTRAL NERVOUS SYSTEM OF THE MONKEY

EXPERIMENTAL ENQUIRY UPON THE AFFERENT TRACTS OF THE CENTRAL NERVOUS SYSTEM OF THE MONKEY Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 BRAIN. PART I., 1895. ©ripral %xtUUs m\h CUniral fees. EXPEEIMENTAL ENQUIEY UPON THE AFFEBENT TEACTS OF THE CENTEAL NEEVOUS SYSTEM OF THE MONKEY. BY F. W. MOTT, M.D. Lecturer on Physiology at Charing Cross Hospital. Introduction.—Since the adoption of the Marchi method for tracing the course of degenerating fibres in the cen- tral nervous system, many results have been obtained which were not capable of demonstration by the previous methods of Weigert and Pal. We can now follow single degenerated fibres in their course, and provided all sources of fallacy, such as mistaking every black dot for a degene- rated fibre, be avoided, the method is a most valuable one ; but in order to ensure correct results with such a very sensitive method, no pains must be spared to ensure the elimination of all possible sources of fallacy. From a long experience, I have concluded that in order to distinguish between black particles and degenerated fibres in transverse section, it is essential so to cut the sections that in some part of their course these degenerated fibres can be seen in vertical section, or in sections which display a length of the degenerated nerve fibres. Since probably every degene- rated fibre will show itself, great care must be taken in the operative procedure; firstly, the wound must be and remain perfectly aseptic; secondly, the antiseptic precautions VOL. XVIII. 1 Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 2 ORIGINAL ARTICLES AND CLINICAL CASES. used must be of a non-irritating character (I always use boiled saline solution) ; thirdly, the lesion must be limited to the structures which are to be experimented upon, for in opening the spinal canal, especially of small animals, it is extremely easy to damage roots which should be left intact, and to compress the cord; lastly, in cutting roots it must be remembered how very easy it is in certain situations, even with the greatest care to injure the cord, and that in dividing roots unilaterally, especially when a larger number are cut, it is often unavoidable not to inter- fere with the vascular supply of the posterior part of that half of the spinal cord. Again, there seems to be some evidence to show that certain fibres degenerate when cut off from their trophic centre at different rates. By considering these possible fallacies many degenerations which have lately been described may probably be explained away. The experi- ments will be found to fall into three groups, A, B, and C, as below. A.—Summary of results of experiments upon unilateral section of roots of the lumbo-sacral region of the spinal cord in seven monkeys and one cat. Degenerated fibres do not pass into the opposite posterior column, nor do they probably enter directly into any of the long ascending tracts of the anterior or lateral columns. In the upper part of the cord the degeneration is limited abso- lutely to the posterior median column of the same side. These facts are proved by three successful cases in which presumably none of the possible fallacies occurred; therefore the degeneration was strictly limited to the part mentioned. These were Cases 1, 2, 3 (vide infra). The degeneration that was found in four cases, and which made me believe at first that fibres passed directly into the opposite antero-lateral tract may probably be explained by one of the fallacies mentioned. In Cases 5, 6 and 7 there was degeneration in the opposite posterior column readily explicable by accidental causes. Goll's column is formed principally by fibres from the fifth, sixth and seventh post-thoracic roots, but some fibres forming a small triangle posteriorly come presumably from the tail. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OF THE MONKEY. o I am indebted to my friend Dr. Sherrington, with whom I am now carrying on further observations on this subject for material of some of the subjoined cases. (Vide fig. 1 and plate I., photo-micrographs 1, 2, 3, 4.) EXPERIMENT I.—Unilateral section of all the posterior roots below the third lumbar on the right side. The animal was kept alive for two months, and the spinal cord hardened in Miiller's fluid, and sections stained by Marchi fluid were cut in celloidin. The following degenerations were noticed :—The whole posterior column of the same side degene- rated as high as the second lumbar, then healthy fibres began to appear in the postero-external column. There was wo degenera- tion in the opposite posterior column nor in the lateral columns above the lesion, nor in the cross pyramidal tracts below the third lumbar. EXPERIMENT II.—Section of the large sixth sub- thoracic posterior root on the right side, below the level of the spinal cord. This is a very important root, as the degeneration shows in the formation of the posterior column in the lumbo-sacral region, and its fibres enter largely into the formation of Goll's column. The animal was kept alive a fortnight; absolutely no degenera- tion was observed in any other part of the cord above the lesion than in the posterior column of the same side. (Photo-micro- graph, plate I., 2.) EXPERIMENT III.—Cat. Unilateral section of the pos- terior spinal ganglia, fifth, sixth, seventh, eighth and ninth post-thoracic roots. No degeneration except in the posterior column of the same side. Animal kept alive forty days. EXPERIMENT IV.—Unilateral section of fifth, sixth, and seventh post-thoracic roots. Animal kept alive ten days. Degeneration in opposite posterior column, and in cross- pyramidal tracts below lesion and in lateral columns above lesion a scattered degeneration. This was probably due, as results show, to pressure on the cord during the operation, or subse- quently from inflammatory products. EXPERIMENT V.—Unilateral section of the third, fourth, fifth, sixth, seventh, eighth and ninth sub-thoracic in a monkey. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 4 ORIGINAL ARTICLES AND CLINICAL CASES. Animal kept alive one month. Degeneration limited to the posterior column of same side above lesion. (Micro-photograph 1, plate I.) No degeneration in opposite posterior column. About thirty degenerated fibres in the situation of Gower's tract in the opposite lateral column. (See plate I.) At first I thought that the only explanation of the presence of these fibres was that pos- terior root fibres pass directly through the anterior commissure to the opposite antero-lateral column, but their absence in Cases 1, 2, and 3 leads me to suspect that some cells in the grey matter have undergone degenerative changes, and consequently fibres which arise from these cells have degenerated upwards and can be traced as far as the corpora quadrigemina. In Experiment I. a larger number of roots were divided, and yet there was no trace of this tract of degeneration. We are, therefore, not warranted in assuming more than that impulses do pass from the posterior roots of the right side to the left corpora quadrigemina by these thirty odd fibres, which we find degenerated as a result of the operation. Possibly thrombosis of a vessel running up the pos- terior roots and supplying a group of nerve cells in connection with these posterior roots below and with the antero-lateral fibres of the opposite side above may be the explanation. EXPERIMENT VI.—Unilateral section on the right side of third, fourth, fifth, sixth, and seventh posterior roots in a monkey. Animal kept alive eighteen days. Degeneration in both antero-lateral columns above lesion and in posterior column of opposite side. This was caused by injury of the sixth sub- thoracic root on the left side in opening the spinal canal. (Plate I., photo-micrograph 3). EXPERIMENT VII.—Unilateral section of the fourth post- thoracic nerve, outside the dura mater. Animal kept alive ten days. I found very little degeneration in the column of Goll of the same side in the cervical region. EXPERIMENT VIII.—Unilateral section of the fourth, fifth, sixth, seventh, eighth and ninth sub-thoracic roots, Animal kept alive two months. Scattered degenerated fibres in both antero-lateral columns above the lesion, a very few fibres in the opposite posterior column. The degenerated fibres in the opposite antero-lateral tract were about thirty in number, and could be traced as far as the corpora quad- rigemina. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OF THE MONKEY. 5 ,thn / Medulla 4- Cervical FIG . 1. Representation of degeneration resulting from unilateral section of a 1 f I J_" * A £ i.' £ 1 T— 1 1 I f t TTT ^ & \ Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 (l ORIGINAL ARTICLES AND CLINICAL CASES. With regard to the results of these experiments I feel convinced that fibres do not pass into the opposite posterior columns from the roots which I have cut in these eight cases. When fibres are found degenerated in the crossed afferent tract of Gowers and Edinger, I would rather explain the degeneration by vascular changes in the grey matter of the posterior horn, than by supposing that fibres from the posterior roots pass directly across to ascend the cord and reach the corpora quadrigemina. On the whole the results of my experiments do not confirm the results of Lowenthal, Berdez, Oddi and Eossi and others, who have found exten- sive degeneration elsewhere than the posterior column of the same side. These experiments rather confirm the results of my previous experiments on monkeys. I found, more- over, that if all the nerve roots entering into the formation of the lumbo sacral plexus, be divided from the third downwards, just above the uppermost cut root, the whole of the posterior column of the same side will be degenerated (vide photo-micrograph 1, plate. i.),but as soon as the fibres of an uncut nerve enter they occupy the part of the column nearest the grey matter. While one group of the degenerated fibres passes forwards and upwards into Clarke's column, ending in a brush work around the vesicular cells, the other group of fibres passes medianwards and back- wards to reach the column of Goll, in which they ascend vertically, and the fibres that enter by the lowest roots take up apparently the most posterior position. B.—Summary of results of median section of the spinal cord in the lumbar region in two monkeys (fig. 2). B . EXPERIMENT I.—Median section of the spinal cord for f in., involving the last dorsal and upper three lumbar- segments. EXPERIMENT II.—Median section for about \ in., involv- ing third, fourth and fifth lumbar segments. The operations were performed with strict antiseptic pre- cautions, and all the while the animals lived no evidence of hyperaesthesia was observed. In both cases, however, the lower limbs were considerably enfeebled, both in sensibility and move- Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OP THE MONKEY. 7 ment. In Case 1, since the section was not quite in the mid-line, the gray matter of one side was considerably damaged and the Pons I Corp quad O/)(ic thalamus FIG . 2. Degenerations resulting from median longitudinal section of the spinal cord in the lumbar region (P. W. M.). Symmetrical ascending degeneration in the antero-lateral ascending tracts. One tract (ventral cerebellar) goes to the vermis vac, the other to corpora quadrigemina. limb of the corresponding side was more paralysed and certainly less sensitive. It was, moreover, swollen, probably owing to Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 8 OBIGINAL ARTICLES AND CLINICAL CASES. vaso-rnotor disturbance. I adopted the same methods for ex- amining, microscopically, the results, as in the previous related experiments. I n Experiment I., the lesion was not in the mid-line, but involved the anterior and posterior horn of the left side, not injuring the grey matter of the right side at all. There was symmetrical degeneration in the antero-lateral column of both sides, not so, however, of the direct cerebellar tract, which was much more extensively degenerated on the left side—the side of injury of the grey matter. This lesion was higher than the next, involving the last dorsal segment, and therefore the lower end of the posterior vesicular column of Clarke. (Vide photo-micrograph 4, plate I.). I n Experiment II., the lesion was much more in the mid- line and was situated below the position of Clarke's column. There was very little degeneration of the direct cerebellar tract, but symmetrical degeneration of the antero-lateral ascend- ing tracts. On examining sections of these spinal cords in the cervical region (see fig. 2), it can be observed that there are two distinct sets of fibres degenerated, one (the more extensive) occupying especially the periphery, ventral cerebellar, the other much smaller stretching backwards and inwards, separated from the former by healthy fibres. This latter tract corresponds in position to the tract of fibres, observed in the opposite antero- lateral column in some of the cases of unilateral section of posterior roots, except that the number of degenerated fibres is much more numerous. The ventral cerebellar tract in the monkey, as I have already shown,* can be traced to the middle lobe of the cerebellum forming a loop over the fifth nerve and turning downwards and backwards on the posterior surface of the superior cerebellar peduncle to reach its destination. The other set of ascending fibres could be traced upwards as far as the superior corpora quadrigemina lying outside the fibres of the lateral fillet, a few apparently going on with the fibres of the fillet to the optic thalamus. This is in all probability the crossed sensory tract of Edinger. C. Summary of Experiments of Unilateral Separation of the Nuclei of the Posterior Columns from the Arciform Fibres issuing therefrom.—Five experiments on monkeys, which * Ref. 5. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 PLATE J. DEGENERATIONS PROM UNILATERAL SECTION OF POSTERIOR ROOTS. Unilateral section of posterior roots in the monkey. (1) Spinal cord at level of third lumbar after unilateral section of posterior roots of cauda oquina, experiment v. Degeneration only in posterior column of same side. (2) Section of the sixth subthoracic root (first sacral man.) Degeneration of posterior column in the upper part of lumbar enlargement, experiment ii. (3) Degeneration of Goll's column; cervical enlargements after unilateral section of posterior roots of cauda equina. (4) The degeneration found in the upper dorsal region after median section. Bxp. I.B. The lesion was not quite in the mid-line, and involved the lower end of Clarke's column, Thero is in consequence degeneration of the direct cerebellar tract. F. W. MOTT. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTBAL NERVOUS SYSTEM OF THE MONKEY. 9 Lumbar Pons I /V//7 FIG . 3. Degenerations in the internal arciform fibres, interolivary layer and of the fillet of the opposite side, following unilateral separation of the posterior column nuclei (F. W. M.). The degenerated fibres represented by black dots can be followed as high as the optic thalamus when they end amid the skin medullares. In some cases of extensive lesions there was a degeneration down the cord probably due to injury of ground fibres. This degeneration is represented in the antero-lateral column of the lumbar region; some are seen decussating in the anterior commissure. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 1 0 ORIGINAL ARTICLES AND CLINICAL CASES. produced the following results of degeneration illustrated by fig. 3, plates II. and II . A, viz., degeneration of the arciform fibres issuing from Goll's nucleus and Burdach's nucleus, which decussate across the mid-line to the opposite inter- olivary layer, forming in the upper part of the medulla a triangular area of degeneration. In the upper part of the pons the degenerated fibres are seen in the median and lateral fillet; probably some of the fibres in the lateral fillet terminate in the corp. quad., while others (more numerous) especially those of the median portion, can be traced onwards to the optic thaalmus, where they spread out and terminate in that mass of grey matter passing through the strice medullares. In not one of these five cases could I satisfy myself that there was a direct continuity of these degenerated fibres by a cortical fillet with the cortex cerebri. In fact, they all seemed to terminate in the optic thalamus. In two cases the injury extended rather deeper and higher, involving the ground fibres and some of the cranial nuclei situated in the floor of the fourth ventricle, and a consider- able degeneration was noted in consequence in the spinal cord below the lesion in the anterior columns, extending down to the lumbo-sacral region. Most of these fibres decussate in the anterior commissure. (See fig. 3.) At first I thought that these might be due to inj ury of the resti- form body, in accordance with the views of Marchi, but the researches of Ferrier and Turner, and Eisien Russell14 on the cerebellum appear to have entirely disproved Marchi's results. I will not describe each experiment, as they were all conducted with one object, although sometimes more, sometimes less was done than intended. The following was the mode of procedure:— As in all the other cases of course the animal was deeply anasthe- tised, and the part to be operated upon shaved and rendered thoroughly aseptic. An incision extending from the occipital protuberance down the neck in the mid-line for about one and a-half inches was made. The muscles attached to the occiput were separated from the bone until the occipito-atloid ligament was exposed. This was cut close to the bone all round. By keeping the neck well extended the floor of the fourth ventricle Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OF THE MONKEY. 11 was exposed, so that one could see the lower part of the pos- terior surface of the medulla and the tip of the middle lobe of the cerebellum. A small, specially-constructed knife, bent at a suitable angle, was inserted into the lower part of the medulla to one side of the mid-line and thrust upwards so as just to cut away, unilaterally, the posterior column nuclei from their con- nections. In all cases the lesion was unilateral and was not com- plicated by any haemorrhage or any difficulties. Nothing but sterile saline solution was used after exposing the occipito- atloid ligament—the muscles and the skin were sewed with horse-hair sutures and a collodion dressing applied. The wounds healed invariably by first intention and remained aseptic. The physiological results were difficult to observe, but it seemed to me quite evident that in extensive lesions the animal did not use the hand of the same side with the same facility as on the opposite side. There was no pyramidal degeneration in most of these cases to account for this. With regard to sensation, it was quite impossible to say anything definite. In the notes of two of the cases I find that I remarked distinct lowering of sensibility on the side of the lesion. The degeneration which results from this lesion is exemplified in fig. 3, and in the photo-micrographs, plate II . and plate II . A. The brains and spinal cords of these five animals were hardened in Miiller's fluid, stained by Marchi's method, and the whole of the central nervous system above the lesion, examined microscopically by serial sections, except the frontal lobes and the occipital lobes. This represents, of course, an immense amount of labour and the preparation of a great number of sections.* COMPARISON OF EESULT S WITH PREVIOUS OBSERVATIONS AND EXPERIMENTS . The experiments performed on the fibres of the posterior roots in monkeys confirm the results I obtained previously by the Weigert method, and agree with those of Singer2 in the dog. I have made these experiments and obser- vations in order to ascertain if Lowenthal,3 Berdez,4 and Oddi4 and Rossi's experiments and observations are to * The sections from Experiments A, B, and C were shown at a meeting of the Physiological Society, held at Charing Cross Hospital Medical School, December, 1893, and at the Physiological Section of the British Association held at Oxford, 1894. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 1-J ORIGINAL ARTICLES AND CLINICAL CASES. be relied upon as showing that fibres pass directly into the long ascending tracts of the lateral columns and the opposite posterior column. Inasmuch as three of my cases failed to show such degeneration in the lateral columns, and four of my cases uncomplicated by injury of roots of the other side did not show any degenerated fibres in the opposite posterior column, I must conclude that probably some fallacy has existed. In fact, one of Lowenthal's cases is obviously fallacious, because there was considerable injury of the posterior horn. Lowenthal divided one or several posterior roots in various regions of the spinal cord in dogs, rabbits, and guinea-pigs. Stained by Marchi's method, his sections showed in the anterior commissure and in the anterior ground bundle, a degeneration which could be traced up the cord to the cervical region, gradually becoming less and less, and situated more at the periphery, also degenerated fibres of posterior column of same side and scattered degenerated fibres of the opposite posterior columns, but less numerous ; degeneration of ventral cerebellar tracts of both sides more marked on the side of the lesion; and degeneration of intermedio-lateral tract on both sides. I cannot speak about sections of roots above the third lumbar, but I can certainly say that unilateral section of the large sixth sub-thoracic root—the unilateral excision of five ganglia in the cat and the section of the whole of the posterior roots entering into the formation of the lumbo-sacral and coccygeal plexuses on one side, produced no such degenerations—the only long fibres degenerated in these cases being the pos- terior column fibres of the same side.* Oddi4 and Eossi have described degenerated fibres in the opposite posterior column. Berdez divided roots on one side in guinea-pigs. Some of the lesions injured the posterior horn and posterior columns, but Berdez concludes from his researches that fibres pass into both lateral columns and into the opposite posterior column. * Of course, it might be urged that the animal (Experiment I.) was kept alive too long to reveal the degeneration well, but that cannot be said of Experiment II. Again, that there are individual peculiarities in structure in different animals. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NEKVOUS SYSTEM OF THE MONKEY. 13 There is no doubt that these observers found degenerated fibres in the situations described, but I cannot help thinking that their presence can be explained by some such accidental cause as I mentioned in the commencement of my paper. At first I believed that some few fibres did pass directly into the antero-lateral columns, but as I could not find thevi in every case I must conclude that these degenerated fibres come from cells in the grey matter. I think the results of median sections, as well as the presence of degenerated fibres on the opposite side in one case after a strictly unilateral root lesion, show that Edinger' and Gowers are right in supposing that there is a path for afferent impressions from the pos- terior roots through cells of the grey matter, and by fibres from the latter which decussate in the anterior commissure and arrive in the antero-lateral tracts, then ascend the cord and course in or near the lateral fillet, terminating in the corpora quadrigemina, and perhaps some few going into the thalamus. I cannot, however, agree with the assumption that this tract conveys painful impressions (Gowers). Its functions are not known. I have6 divided the antero-lateral portions of the cord in the monkey on one and on both sides without any obvious effect on sensation. Lately Bechterew7 has shown that section of the anterior half of the cord pro- duces little or no effect on sensation in the dog. He finds that the only way to produce a complete block to sensory impulses is to cut through both lateral columns and the posterior half of the cord as well. Bottarzi26 working with Luciani, has obtained similar results in dogs to those which I obtained in monkeys after hemisection of the spinal cord. Brown-Sequard8 himself has entirely renounced his view that the group of clinical symptoms which bears his illus- trious name, and which results from unilateral stabs or wounds of the spinal cord (whether they be hemisections or not) can be explained by the immediate decussation of sensory impulses ; indeed, just prior to his death he pub- lished a paper setting forth his later experiments and reasons why he had entirely renounced his former hypo- thesis. We seem indeed to be coming back to the views of Schiff Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 1 4 ORIGINAL ARTICLES AND CLINICAL CASES. that the grey matter conducts painful sensations and heat and cold, whilst the posterior columns convey the tactile and muscular sense impressions. This is strongly supported by the observations made in recent years upon syringomyelia. The fact I have above shown that that portion of the antero-lateral tract which can be traced to the vermis, and which is also symmetrically degenerated by median sections even when the grey matter of one side is seriously injured, the other side not, agrees with the results of Auerbach,9 who found that destruction in the cat of a considerable length of one half of the spinal cord, including the posterior white column, the posterior horn of grey matter and the posterior part of the lateral column, is followed by ascending degene- ration in the direct cerebellar tract of the same side and the antero-lateral cerebellar tract of the opposite, which he, like Lowenthal and myself, traces to the vermis. I n the median sections of the cord the antero-lateral fibres are seen to consist of two distinct tracts, one the crossed afferent tract of Edinger, the other a crossed cere- bellar tract. I have shown that these tracts must arise from cells in the grey matter (perhaps at the base of the anterior horn), that they give off fibres which decussate in the anterior commissure; if they did not decussate then (like the direct cerebellar tract in the case in which the section was not in the mid-line, but involved the gray matter of one side), the degeneration of these two antero-lateral ascending tracts would not be equal and symmetrical on the two sides, but much more on the side in which the grey matter was de- stroyed. This inference is supported, moreover, by the experiments of Ehrlich and Brieger,10 and Singer11 and Miin- zer, viz., compression of the abdominal aorta in rabbits causes necrosis of the nerve cells in the lumbar spinal cord, and ascending degeneration in the antero-lateral ascending tract. I t has been inferred by the latter two observers that this tract arises from the cells of the grey matter of the lumbar region. Vide also a paper by A. S. Griinbaum,12 who con- firms the observations of Auerbach and Singer and Miinzer, but his observations are limited to the cord. H e considers as the result of his two experiments of Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OF THE MONKEY. 15 longitudinal division of the spinal cord in the cat that the anterior commissure fibres go in part to the antero-lateral column, and at the same time derive their origin from the grey matter of the opposite side. Schiifer25 has figured fibres of the antero-lateral tract going to the corpora quadrigemina after hemisection of the spinal cord in the monkey. TH E POSTERIOR COLUMN NUCLEI AND THE FILLET. A large and important literature exists upon the fillet based upon embryological and pathological data. For a full account, vide Flechsig and Hosel,15 Mahaim,10 Bruce,17 Dejerine,18 Von Monakow,19 but as my paper is solely an ex- perimental enquiry I shall only refer here especially to ex- perimental evidence upon the origin and course of the fibres arising from the posterior column nuclei. Von Vejas20 discovered that after destroying the posterior column nuclei in new born animals there occurred an atrophy of the internal arciform fibres of the same side, atrophy of the inter-olivary layer of the opposite side, and atrophy of the fillet, which could be followed up as high as the corpus trapezoides. Lastly, Singer and Miinzer,21 after experimental destruction of the nuclei of Burdach found atrophy of the internal arciform fibres, and a demonstrable atrophy of the fillet of the opposite side which could be followed up to the optic thalamus.* Monakow19 found after destruction of the parietal lobe in young animals atrophy of the fillet, of the internal arciform fibres of the opposite side, and of the nucleus gracilis of the opposite side. This, certainly, taken with the observations of Flechsig and Hosel upon a case of porencephalic defect of the central convolutions which was associated with atrophy of the fillet of the same side and of the internal arciform fibres and the posterior column nuclei of the oppo- site side, shows that the fillet may degenerate downwards * I am informed by Dr. Turner that, in conjunction with Professor Perrier their experiments showed that the fillet terminated in the optic thalamus. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 1 6 ORIGINAL ARTICLES AND CLINICAL CASES. and that the posterior column nuclei are in direct connec- tion (or indirect connection through the thalamus) with the central convolutions of the cortex. As I was unable to trace any degeneration beyond the optic thalamus, or to find any evidence of a degenerated cortical fillet, I should be inclined to agree with Mahaim and Monakow that the posterior column nuclei stand in connection with the optic thalamus by the fillet, and each portion of the thalamus is in relation to a definite part of the cortex, especially as he, Monakow, finds that the de- generation may proceed down to the posterior column nuclei leading to their atrophy and destruction; may not, therefore, the cells in the optic thalamus undergo a similar atrophy and disappearance ? The work of Flechsig and Hosel is, how- ever, of very great importance, because it shows that an affe- rent tract carrying sensory impulses from the periphery is in connection with what is called the " motor area," and which, therefore, cannot be purely motor. The internal arciform fibres form two groups, one coming from Goll's nucleus and decussating at a lower level, the other coming fromBurdach's nucleus. I am inclined to think, in contradistinction to Bechterew that the fibres proceeding from Goll's nucleus enter more into the formation of what is called the lateral fillet. I am of opinion that the distinction of different fillets is artificial, for it seems to me that the fibres of the so-called lateral fillet are fibres which are taking an oblique instead of a vertical direction. It is impossible to localise a lesion to Goll's nucleus, or to Burdach's nucleus alone, but I have formed this opinion from examination and com- parison of sections in which these two nuclei have been unequally injured, and by other facts which, if confirmed by further observations, would render the supposition that fibres issuing from Goll's nucleus enter into the formation of the lateral fillet still more probable. With regard to the degenerated fibres which descend the cord, many of which decussate in the anterior com- missure, it is very possible, as suggested by Ferrier and Turner, that these come from Deiter's nucleus which is in relation with the semi-circular canals by the external branch Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 PLATE II. POSTERIOR COLUMN NUCLEI LESIONS—PRODUCING DEGENERATION OF FILLET. l . 2. Lesions of medulla separating the posterior column nuclei from the arciform fibres issuing therefrom. (1) Lesion of nucleus gracilis showing the degenerated arciform fibres decussating to take up a position between the olive and pyramid. (2) Lesion higher up and separating Burdach's nucleus from the arciform fibres that issue from it. These degenerated fibres can be traced on the right hand side as the internal arciform fibres which sweep round behind the olive of the same side to reach the opposite interolivary layer. (8) Interolivary layer in the upper part of the medulla magnified about 80 diameters, composed of almost entirely black degenerated fibres, lying between the oliva and the pyramid. (4) Fillet above the lesion on the opposite side, and stained very black on account of the large number of degenerated fibres. Section from the upper part of pons varolii. P . W . JIOTT. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 PLATE II. A. Degeneration of fillet following lesions of posterior column nuclei. 5) Section of the pons at junction with crus cerebri magnified five diameters, (5) e degeneration of the fillet in the section is quite visible to the naked eye, Th but it is extremely difficult to photograph with such low magnification, but still it will be observed that the fillet is much blacker on one side than the other. (6) Section of optic thalamus showing degenerated fibres of fillet now taking a longitudinal and spreading course to end in the grey matter of this ganglion. P. W. UOTT. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OF THE MONKEY. 17 of the auditory nerve, and these fibres which degenerate downwards in the cord convey impulses from that nucleus connected with equilibration down to the anterior horn cells of the lumbo-sacral region, which of course in the monkey, like man, would preside over the muscles connected with movements and position in space. Certainly these fibres do not come directly from the cerebellum as Marchi22 sup- posed. This degeneration was extremely well marked in one case in which the lesion was extensive and involved Deiter's nucleus and other cranial nuclei, including the sixth (to the injury of which I attributed an upward degeneration in the posterior longitudinal bundle, of the opposite side mainly), extending as high as the third nucleus. These fibres may also possibly be ground fibres from motor cranial nuclei, particularly the ocular nuclei, and serving as bridges between spinal and cranial nuclei, in co-ordinate reflex movements directed by vision. Summary of results are shown in the three figs. 1, 2, 3, but- I shall briefly recapitulate the results of the fourteen experiments. (1) The column of Goll is formed especially by the fifth, sixth and seventh sub-thoracic roots. Section of the fourth sub-thoracic posterior root produced comparatively little degeneration of Goll's column (Experiment VII.), and further experiments which Dr. Sherrington and I have made show, as I anticipated, that few fibres enter into the formation of Goll's column above the fourth sub-thoracic. After uncomplicated unilateral section even of a large num- ber of roots, there is no degeneration in the opposite posterior column. The tract of Goll ends in the nucleus of the funi- culus gracilis. When this nucleus is destroyed, or the fibres issuing from it separated from the cells of the nucleus, a degeneration occurs in the internal arciform fibres, the opposite inter-olivary layer and fillet, which can be traced tip to the optic thalamus. It is impossible to injure Goll's nucleus without Burdach's nucleus being involved, and I found experimentally that the greater number of the fibres of the fillet come from the latter nucleus. In no case could degenerated fibres be traced to the cortex. VOL. XVIII. 2 Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 1 8 ORIGINAL ARTICLES AND CLINICAL CASES. (2) After unilateral section of roots in most instances degenerated fibres were found in the opposite antero-lateral column, but inasmuch as they were not always present in every case, I assume that these fibres come from cells of the grey matter of the same side as the lesion and cross over in the anterior commissure, and it is possible that cells from which, in all probability, these fibres arise are damaged by vascular changes in the grey matter—the result of the operation. These fibres form a tract internal to the ventral cerebellar tract, and in no case were the}' above forty in number even after section of eight posterior sub-thoracic roots. Some few degenerated fibres were observed in most cases in the lateral column of the same side ; none, how- ever, in the direct cerebellar tracts after section of roots below the second lumbar. In connection with this subject vide a preliminary com- munication by J. N. Langley 23 and H. K. Anderson. (3) After median section in the lumbar region for three- quarters of an inch, there was a symmetrical degeneration in the antero-lateral tract of the two sides. The fibres con- sist of two sets: (1) The ventral cerebellar, much the more numerous and situated most peripherally, which can be traced to the vermis, looping over the fifth nerve to reach the superior cerebellar peduncle, and then descending on its posterior aspect to the middle lobe of the cerebellum. (2) The crossed afferent tract of Gowers and Edinger (function unknown), which, in all probability, arises from cells of the grey matter, its fibres decussating in the anterior commis- sure. These fibres occupy exactly the same position, but are much more numerous than the small tract which was observed after unilateral section of roots. They can be traced right up the cord and the medulla in the pons varolii, above this lying to the outside of the lateral fillet, and ter- minating in the corpora quadrigemina, some few apparently extending to the optic thalamus. Ramon y Cajal24 has shown that fibres arise from cells at the base of the anterior horn, and decussate in the anterior commissure. It is, therefore, possible that these cells are the source of origin of these two ascending tracts. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OP THE MONKEY. 19 In one case of median section the last dorsal segment was injured, and on the same side there was a very ex- tensive degeneration of the direct cerebellar tract. The fact that the ventral cerebellar tract is equal and symmetrical in these vertical -lesions whether the incision occupies the mid-line or not, shows that it, like the crossed afferent tract of Edinger, is a crossed cerebellar tract coming from the cells of the grey matter, possibly at the base of the anterior horn. REFERENCES. 1 MOTT. " The Bipolar Cells of the Spinal Cord and their connections," BRAIN, 1890. 2. SINGER, J. " Ueber secundiiro Degeneration in Riickenmarke des Hundes," Sitzimgsbcrichtc der Wiener Akacl., Bd. lxxxiv., Abth. iii., 3. LOWENTHAL. International iTonatschrift f. Anat. und Physiol., 1893, Bd. x. 4. ODDI et Rossi. " Sur les cours des voies afferentes de la moe'lle epiniere," Archives Ital. de Jiiol., xv., 1891. BERDEZ. "Recherches experimentales sur le trajet des fibres ccntri- petes dans la moiille epiniere," Iici-ue Mcd. de la Suisse Romandc, 0. EDINGER. " Einiges von Vevlauf der Gefiihlsbahnen in Centralen Nervensystems," Deutsche Hcd. Wochenschrift, 1890. C. MOTT. " Ascending Degenerations resulting from Lesions of the Spinal Cord in Monkeys," BBAIN, 1892. " Results of Hemisection of tlic Spinal Cord in Monkeys," Phil. Trans., B., 1891. 7. BECHTEREW. " Die sensiblun Bahuen irn Ruckenmark nach den Untersuchungen von Dr. P. Holzinger." 8. BHOWN-SKQUARD. " Remarques apropos des recherches du Dr. F. \V. Mott sur les effets de la section d'une moitie laterale de la mobile epiniere." 9. AxjEuiiACH, L. " Zur Auat. d. aufsteigenden degenerierenden Systeme des Riickcnmarks." Anat. Anzeiger, 1890. 10. EHRLICH andBniEGEH. " Ueber die Ausschaltung der Lendenmarks," Zcit.f. klin. Mcdicin, vii., 18S4. 11. SISGEB and M0NZP:K. " Beitrag. zur Anat. d. Centralnervensystems iusbesouders des Riickeninarkes," Wiener Dentschr., lvii., 1891. 12. ORCSBAUM, A. S. " Note on tlie I^egcnerations following Double Transverse Longitudinal and Anterior Coruual Lesions of the Spinal .Cord," Journal uf 1'hysiuloyn, May, 1894. 13. PEBRIER and TURNER. " Recent Work on the Cerebellum and its Relations, with Remarks on the Central Connections, &c," BBAIN, part i., 1894. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 2 0 OBIGINAL ARTICLES AND CLINICAL CASES. 14. RISIEN RUSSELL. " Denegerations consequent on Experimental Lesions of the Cerebellum," Brit. Med. Journ., Sept. 22, 1894. 15. FLECHSIG and HOSEL. " Die Central Windungen ein Central organ der Hinterstriinge," Archiv f. Psychiatrie, Bd. xxiv., Heft 8. 16. MAHAIM. "Ein Fall von Secundarer Erkrankung des Thalamus Opticus, &c," Archiv fiir Psychiatrie, Bd. xxv., Heft 2. 17. BBUCE. BEAIN, part lxiv., 1893. 18. DEJEBINE. Archiv de Physiologic, 1890. 19. MONAKOW. Neurol. Centralblatt, 1885, p. 65. 20. VON VEJAS. Archiv f. Psychiatrie, xvi., 1885. 21. SINGES. " Abth. d. math. nat. Klasse d. k.k. Akad. d. Wisseuschaft, Wien, 1890. 22. MABCHI. " Sulle degen consec. alia estirp. totale e parziale del cerveletto," Bit;. Spcr. di Frenatria, 1887. 23. <T. N. LANGLEY, F.E.S., and H. K. ANDEESON. "Notes on Degener- ation resulting from Section of Nerve Roots and Injury to the Spinal Cord," Proceedings of the Physiol. Soc, May 12,1894, Journal of Physiology, vol. xvi., June 5, 1894. 24. RAMON Y CAJAL. Croonian Lecture, March, 1894. 25. SCHAPEB. " Quain's Anatomy," vol. iii., part i., p. 33. 26. BOTTAEZI. Ueber die Hemisection des Riickenmarkes bei Hunden. Centralblatt fiir Physiologic, December 1, 1894. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Brain Unpaywall

EXPERIMENTAL ENQUIRY UPON THE AFFERENT TRACTS OF THE CENTRAL NERVOUS SYSTEM OF THE MONKEY

MOTT, F. W.
Brain – Jan 1, 1895
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Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 BRAIN. PART I., 1895. ©ripral %xtUUs m\h CUniral fees. EXPEEIMENTAL ENQUIEY UPON THE AFFEBENT TEACTS OF THE CENTEAL NEEVOUS SYSTEM OF THE MONKEY. BY F. W. MOTT, M.D. Lecturer on Physiology at Charing Cross Hospital. Introduction.—Since the adoption of the Marchi method for tracing the course of degenerating fibres in the cen- tral nervous system, many results have been obtained which were not capable of demonstration by the previous methods of Weigert and Pal. We can now follow single degenerated fibres in their course, and provided all sources of fallacy, such as mistaking every black dot for a degene- rated fibre, be avoided, the method is a most valuable one ; but in order to ensure correct results with such a very sensitive method, no pains must be spared to ensure the elimination of all possible sources of fallacy. From a long experience, I have concluded that in order to distinguish between black particles and degenerated fibres in transverse section, it is essential so to cut the sections that in some part of their course these degenerated fibres can be seen in vertical section, or in sections which display a length of the degenerated nerve fibres. Since probably every degene- rated fibre will show itself, great care must be taken in the operative procedure; firstly, the wound must be and remain perfectly aseptic; secondly, the antiseptic precautions VOL. XVIII. 1 Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 2 ORIGINAL ARTICLES AND CLINICAL CASES. used must be of a non-irritating character (I always use boiled saline solution) ; thirdly, the lesion must be limited to the structures which are to be experimented upon, for in opening the spinal canal, especially of small animals, it is extremely easy to damage roots which should be left intact, and to compress the cord; lastly, in cutting roots it must be remembered how very easy it is in certain situations, even with the greatest care to injure the cord, and that in dividing roots unilaterally, especially when a larger number are cut, it is often unavoidable not to inter- fere with the vascular supply of the posterior part of that half of the spinal cord. Again, there seems to be some evidence to show that certain fibres degenerate when cut off from their trophic centre at different rates. By considering these possible fallacies many degenerations which have lately been described may probably be explained away. The experi- ments will be found to fall into three groups, A, B, and C, as below. A.—Summary of results of experiments upon unilateral section of roots of the lumbo-sacral region of the spinal cord in seven monkeys and one cat. Degenerated fibres do not pass into the opposite posterior column, nor do they probably enter directly into any of the long ascending tracts of the anterior or lateral columns. In the upper part of the cord the degeneration is limited abso- lutely to the posterior median column of the same side. These facts are proved by three successful cases in which presumably none of the possible fallacies occurred; therefore the degeneration was strictly limited to the part mentioned. These were Cases 1, 2, 3 (vide infra). The degeneration that was found in four cases, and which made me believe at first that fibres passed directly into the opposite antero-lateral tract may probably be explained by one of the fallacies mentioned. In Cases 5, 6 and 7 there was degeneration in the opposite posterior column readily explicable by accidental causes. Goll's column is formed principally by fibres from the fifth, sixth and seventh post-thoracic roots, but some fibres forming a small triangle posteriorly come presumably from the tail. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OF THE MONKEY. o I am indebted to my friend Dr. Sherrington, with whom I am now carrying on further observations on this subject for material of some of the subjoined cases. (Vide fig. 1 and plate I., photo-micrographs 1, 2, 3, 4.) EXPERIMENT I.—Unilateral section of all the posterior roots below the third lumbar on the right side. The animal was kept alive for two months, and the spinal cord hardened in Miiller's fluid, and sections stained by Marchi fluid were cut in celloidin. The following degenerations were noticed :—The whole posterior column of the same side degene- rated as high as the second lumbar, then healthy fibres began to appear in the postero-external column. There was wo degenera- tion in the opposite posterior column nor in the lateral columns above the lesion, nor in the cross pyramidal tracts below the third lumbar. EXPERIMENT II.—Section of the large sixth sub- thoracic posterior root on the right side, below the level of the spinal cord. This is a very important root, as the degeneration shows in the formation of the posterior column in the lumbo-sacral region, and its fibres enter largely into the formation of Goll's column. The animal was kept alive a fortnight; absolutely no degenera- tion was observed in any other part of the cord above the lesion than in the posterior column of the same side. (Photo-micro- graph, plate I., 2.) EXPERIMENT III.—Cat. Unilateral section of the pos- terior spinal ganglia, fifth, sixth, seventh, eighth and ninth post-thoracic roots. No degeneration except in the posterior column of the same side. Animal kept alive forty days. EXPERIMENT IV.—Unilateral section of fifth, sixth, and seventh post-thoracic roots. Animal kept alive ten days. Degeneration in opposite posterior column, and in cross- pyramidal tracts below lesion and in lateral columns above lesion a scattered degeneration. This was probably due, as results show, to pressure on the cord during the operation, or subse- quently from inflammatory products. EXPERIMENT V.—Unilateral section of the third, fourth, fifth, sixth, seventh, eighth and ninth sub-thoracic in a monkey. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 4 ORIGINAL ARTICLES AND CLINICAL CASES. Animal kept alive one month. Degeneration limited to the posterior column of same side above lesion. (Micro-photograph 1, plate I.) No degeneration in opposite posterior column. About thirty degenerated fibres in the situation of Gower's tract in the opposite lateral column. (See plate I.) At first I thought that the only explanation of the presence of these fibres was that pos- terior root fibres pass directly through the anterior commissure to the opposite antero-lateral column, but their absence in Cases 1, 2, and 3 leads me to suspect that some cells in the grey matter have undergone degenerative changes, and consequently fibres which arise from these cells have degenerated upwards and can be traced as far as the corpora quadrigemina. In Experiment I. a larger number of roots were divided, and yet there was no trace of this tract of degeneration. We are, therefore, not warranted in assuming more than that impulses do pass from the posterior roots of the right side to the left corpora quadrigemina by these thirty odd fibres, which we find degenerated as a result of the operation. Possibly thrombosis of a vessel running up the pos- terior roots and supplying a group of nerve cells in connection with these posterior roots below and with the antero-lateral fibres of the opposite side above may be the explanation. EXPERIMENT VI.—Unilateral section on the right side of third, fourth, fifth, sixth, and seventh posterior roots in a monkey. Animal kept alive eighteen days. Degeneration in both antero-lateral columns above lesion and in posterior column of opposite side. This was caused by injury of the sixth sub- thoracic root on the left side in opening the spinal canal. (Plate I., photo-micrograph 3). EXPERIMENT VII.—Unilateral section of the fourth post- thoracic nerve, outside the dura mater. Animal kept alive ten days. I found very little degeneration in the column of Goll of the same side in the cervical region. EXPERIMENT VIII.—Unilateral section of the fourth, fifth, sixth, seventh, eighth and ninth sub-thoracic roots, Animal kept alive two months. Scattered degenerated fibres in both antero-lateral columns above the lesion, a very few fibres in the opposite posterior column. The degenerated fibres in the opposite antero-lateral tract were about thirty in number, and could be traced as far as the corpora quad- rigemina. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OF THE MONKEY. 5 ,thn / Medulla 4- Cervical FIG . 1. Representation of degeneration resulting from unilateral section of a 1 f I J_" * A £ i.' £ 1 T— 1 1 I f t TTT ^ & \ Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 (l ORIGINAL ARTICLES AND CLINICAL CASES. With regard to the results of these experiments I feel convinced that fibres do not pass into the opposite posterior columns from the roots which I have cut in these eight cases. When fibres are found degenerated in the crossed afferent tract of Gowers and Edinger, I would rather explain the degeneration by vascular changes in the grey matter of the posterior horn, than by supposing that fibres from the posterior roots pass directly across to ascend the cord and reach the corpora quadrigemina. On the whole the results of my experiments do not confirm the results of Lowenthal, Berdez, Oddi and Eossi and others, who have found exten- sive degeneration elsewhere than the posterior column of the same side. These experiments rather confirm the results of my previous experiments on monkeys. I found, more- over, that if all the nerve roots entering into the formation of the lumbo sacral plexus, be divided from the third downwards, just above the uppermost cut root, the whole of the posterior column of the same side will be degenerated (vide photo-micrograph 1, plate. i.),but as soon as the fibres of an uncut nerve enter they occupy the part of the column nearest the grey matter. While one group of the degenerated fibres passes forwards and upwards into Clarke's column, ending in a brush work around the vesicular cells, the other group of fibres passes medianwards and back- wards to reach the column of Goll, in which they ascend vertically, and the fibres that enter by the lowest roots take up apparently the most posterior position. B.—Summary of results of median section of the spinal cord in the lumbar region in two monkeys (fig. 2). B . EXPERIMENT I.—Median section of the spinal cord for f in., involving the last dorsal and upper three lumbar- segments. EXPERIMENT II.—Median section for about \ in., involv- ing third, fourth and fifth lumbar segments. The operations were performed with strict antiseptic pre- cautions, and all the while the animals lived no evidence of hyperaesthesia was observed. In both cases, however, the lower limbs were considerably enfeebled, both in sensibility and move- Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OP THE MONKEY. 7 ment. In Case 1, since the section was not quite in the mid-line, the gray matter of one side was considerably damaged and the Pons I Corp quad O/)(ic thalamus FIG . 2. Degenerations resulting from median longitudinal section of the spinal cord in the lumbar region (P. W. M.). Symmetrical ascending degeneration in the antero-lateral ascending tracts. One tract (ventral cerebellar) goes to the vermis vac, the other to corpora quadrigemina. limb of the corresponding side was more paralysed and certainly less sensitive. It was, moreover, swollen, probably owing to Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 8 OBIGINAL ARTICLES AND CLINICAL CASES. vaso-rnotor disturbance. I adopted the same methods for ex- amining, microscopically, the results, as in the previous related experiments. I n Experiment I., the lesion was not in the mid-line, but involved the anterior and posterior horn of the left side, not injuring the grey matter of the right side at all. There was symmetrical degeneration in the antero-lateral column of both sides, not so, however, of the direct cerebellar tract, which was much more extensively degenerated on the left side—the side of injury of the grey matter. This lesion was higher than the next, involving the last dorsal segment, and therefore the lower end of the posterior vesicular column of Clarke. (Vide photo-micrograph 4, plate I.). I n Experiment II., the lesion was much more in the mid- line and was situated below the position of Clarke's column. There was very little degeneration of the direct cerebellar tract, but symmetrical degeneration of the antero-lateral ascend- ing tracts. On examining sections of these spinal cords in the cervical region (see fig. 2), it can be observed that there are two distinct sets of fibres degenerated, one (the more extensive) occupying especially the periphery, ventral cerebellar, the other much smaller stretching backwards and inwards, separated from the former by healthy fibres. This latter tract corresponds in position to the tract of fibres, observed in the opposite antero- lateral column in some of the cases of unilateral section of posterior roots, except that the number of degenerated fibres is much more numerous. The ventral cerebellar tract in the monkey, as I have already shown,* can be traced to the middle lobe of the cerebellum forming a loop over the fifth nerve and turning downwards and backwards on the posterior surface of the superior cerebellar peduncle to reach its destination. The other set of ascending fibres could be traced upwards as far as the superior corpora quadrigemina lying outside the fibres of the lateral fillet, a few apparently going on with the fibres of the fillet to the optic thalamus. This is in all probability the crossed sensory tract of Edinger. C. Summary of Experiments of Unilateral Separation of the Nuclei of the Posterior Columns from the Arciform Fibres issuing therefrom.—Five experiments on monkeys, which * Ref. 5. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 PLATE J. DEGENERATIONS PROM UNILATERAL SECTION OF POSTERIOR ROOTS. Unilateral section of posterior roots in the monkey. (1) Spinal cord at level of third lumbar after unilateral section of posterior roots of cauda oquina, experiment v. Degeneration only in posterior column of same side. (2) Section of the sixth subthoracic root (first sacral man.) Degeneration of posterior column in the upper part of lumbar enlargement, experiment ii. (3) Degeneration of Goll's column; cervical enlargements after unilateral section of posterior roots of cauda equina. (4) The degeneration found in the upper dorsal region after median section. Bxp. I.B. The lesion was not quite in the mid-line, and involved the lower end of Clarke's column, Thero is in consequence degeneration of the direct cerebellar tract. F. W. MOTT. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTBAL NERVOUS SYSTEM OF THE MONKEY. 9 Lumbar Pons I /V//7 FIG . 3. Degenerations in the internal arciform fibres, interolivary layer and of the fillet of the opposite side, following unilateral separation of the posterior column nuclei (F. W. M.). The degenerated fibres represented by black dots can be followed as high as the optic thalamus when they end amid the skin medullares. In some cases of extensive lesions there was a degeneration down the cord probably due to injury of ground fibres. This degeneration is represented in the antero-lateral column of the lumbar region; some are seen decussating in the anterior commissure. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 1 0 ORIGINAL ARTICLES AND CLINICAL CASES. produced the following results of degeneration illustrated by fig. 3, plates II. and II . A, viz., degeneration of the arciform fibres issuing from Goll's nucleus and Burdach's nucleus, which decussate across the mid-line to the opposite inter- olivary layer, forming in the upper part of the medulla a triangular area of degeneration. In the upper part of the pons the degenerated fibres are seen in the median and lateral fillet; probably some of the fibres in the lateral fillet terminate in the corp. quad., while others (more numerous) especially those of the median portion, can be traced onwards to the optic thaalmus, where they spread out and terminate in that mass of grey matter passing through the strice medullares. In not one of these five cases could I satisfy myself that there was a direct continuity of these degenerated fibres by a cortical fillet with the cortex cerebri. In fact, they all seemed to terminate in the optic thalamus. In two cases the injury extended rather deeper and higher, involving the ground fibres and some of the cranial nuclei situated in the floor of the fourth ventricle, and a consider- able degeneration was noted in consequence in the spinal cord below the lesion in the anterior columns, extending down to the lumbo-sacral region. Most of these fibres decussate in the anterior commissure. (See fig. 3.) At first I thought that these might be due to inj ury of the resti- form body, in accordance with the views of Marchi, but the researches of Ferrier and Turner, and Eisien Russell14 on the cerebellum appear to have entirely disproved Marchi's results. I will not describe each experiment, as they were all conducted with one object, although sometimes more, sometimes less was done than intended. The following was the mode of procedure:— As in all the other cases of course the animal was deeply anasthe- tised, and the part to be operated upon shaved and rendered thoroughly aseptic. An incision extending from the occipital protuberance down the neck in the mid-line for about one and a-half inches was made. The muscles attached to the occiput were separated from the bone until the occipito-atloid ligament was exposed. This was cut close to the bone all round. By keeping the neck well extended the floor of the fourth ventricle Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OF THE MONKEY. 11 was exposed, so that one could see the lower part of the pos- terior surface of the medulla and the tip of the middle lobe of the cerebellum. A small, specially-constructed knife, bent at a suitable angle, was inserted into the lower part of the medulla to one side of the mid-line and thrust upwards so as just to cut away, unilaterally, the posterior column nuclei from their con- nections. In all cases the lesion was unilateral and was not com- plicated by any haemorrhage or any difficulties. Nothing but sterile saline solution was used after exposing the occipito- atloid ligament—the muscles and the skin were sewed with horse-hair sutures and a collodion dressing applied. The wounds healed invariably by first intention and remained aseptic. The physiological results were difficult to observe, but it seemed to me quite evident that in extensive lesions the animal did not use the hand of the same side with the same facility as on the opposite side. There was no pyramidal degeneration in most of these cases to account for this. With regard to sensation, it was quite impossible to say anything definite. In the notes of two of the cases I find that I remarked distinct lowering of sensibility on the side of the lesion. The degeneration which results from this lesion is exemplified in fig. 3, and in the photo-micrographs, plate II . and plate II . A. The brains and spinal cords of these five animals were hardened in Miiller's fluid, stained by Marchi's method, and the whole of the central nervous system above the lesion, examined microscopically by serial sections, except the frontal lobes and the occipital lobes. This represents, of course, an immense amount of labour and the preparation of a great number of sections.* COMPARISON OF EESULT S WITH PREVIOUS OBSERVATIONS AND EXPERIMENTS . The experiments performed on the fibres of the posterior roots in monkeys confirm the results I obtained previously by the Weigert method, and agree with those of Singer2 in the dog. I have made these experiments and obser- vations in order to ascertain if Lowenthal,3 Berdez,4 and Oddi4 and Rossi's experiments and observations are to * The sections from Experiments A, B, and C were shown at a meeting of the Physiological Society, held at Charing Cross Hospital Medical School, December, 1893, and at the Physiological Section of the British Association held at Oxford, 1894. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 1-J ORIGINAL ARTICLES AND CLINICAL CASES. be relied upon as showing that fibres pass directly into the long ascending tracts of the lateral columns and the opposite posterior column. Inasmuch as three of my cases failed to show such degeneration in the lateral columns, and four of my cases uncomplicated by injury of roots of the other side did not show any degenerated fibres in the opposite posterior column, I must conclude that probably some fallacy has existed. In fact, one of Lowenthal's cases is obviously fallacious, because there was considerable injury of the posterior horn. Lowenthal divided one or several posterior roots in various regions of the spinal cord in dogs, rabbits, and guinea-pigs. Stained by Marchi's method, his sections showed in the anterior commissure and in the anterior ground bundle, a degeneration which could be traced up the cord to the cervical region, gradually becoming less and less, and situated more at the periphery, also degenerated fibres of posterior column of same side and scattered degenerated fibres of the opposite posterior columns, but less numerous ; degeneration of ventral cerebellar tracts of both sides more marked on the side of the lesion; and degeneration of intermedio-lateral tract on both sides. I cannot speak about sections of roots above the third lumbar, but I can certainly say that unilateral section of the large sixth sub-thoracic root—the unilateral excision of five ganglia in the cat and the section of the whole of the posterior roots entering into the formation of the lumbo-sacral and coccygeal plexuses on one side, produced no such degenerations—the only long fibres degenerated in these cases being the pos- terior column fibres of the same side.* Oddi4 and Eossi have described degenerated fibres in the opposite posterior column. Berdez divided roots on one side in guinea-pigs. Some of the lesions injured the posterior horn and posterior columns, but Berdez concludes from his researches that fibres pass into both lateral columns and into the opposite posterior column. * Of course, it might be urged that the animal (Experiment I.) was kept alive too long to reveal the degeneration well, but that cannot be said of Experiment II. Again, that there are individual peculiarities in structure in different animals. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NEKVOUS SYSTEM OF THE MONKEY. 13 There is no doubt that these observers found degenerated fibres in the situations described, but I cannot help thinking that their presence can be explained by some such accidental cause as I mentioned in the commencement of my paper. At first I believed that some few fibres did pass directly into the antero-lateral columns, but as I could not find thevi in every case I must conclude that these degenerated fibres come from cells in the grey matter. I think the results of median sections, as well as the presence of degenerated fibres on the opposite side in one case after a strictly unilateral root lesion, show that Edinger' and Gowers are right in supposing that there is a path for afferent impressions from the pos- terior roots through cells of the grey matter, and by fibres from the latter which decussate in the anterior commissure and arrive in the antero-lateral tracts, then ascend the cord and course in or near the lateral fillet, terminating in the corpora quadrigemina, and perhaps some few going into the thalamus. I cannot, however, agree with the assumption that this tract conveys painful impressions (Gowers). Its functions are not known. I have6 divided the antero-lateral portions of the cord in the monkey on one and on both sides without any obvious effect on sensation. Lately Bechterew7 has shown that section of the anterior half of the cord pro- duces little or no effect on sensation in the dog. He finds that the only way to produce a complete block to sensory impulses is to cut through both lateral columns and the posterior half of the cord as well. Bottarzi26 working with Luciani, has obtained similar results in dogs to those which I obtained in monkeys after hemisection of the spinal cord. Brown-Sequard8 himself has entirely renounced his view that the group of clinical symptoms which bears his illus- trious name, and which results from unilateral stabs or wounds of the spinal cord (whether they be hemisections or not) can be explained by the immediate decussation of sensory impulses ; indeed, just prior to his death he pub- lished a paper setting forth his later experiments and reasons why he had entirely renounced his former hypo- thesis. We seem indeed to be coming back to the views of Schiff Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 1 4 ORIGINAL ARTICLES AND CLINICAL CASES. that the grey matter conducts painful sensations and heat and cold, whilst the posterior columns convey the tactile and muscular sense impressions. This is strongly supported by the observations made in recent years upon syringomyelia. The fact I have above shown that that portion of the antero-lateral tract which can be traced to the vermis, and which is also symmetrically degenerated by median sections even when the grey matter of one side is seriously injured, the other side not, agrees with the results of Auerbach,9 who found that destruction in the cat of a considerable length of one half of the spinal cord, including the posterior white column, the posterior horn of grey matter and the posterior part of the lateral column, is followed by ascending degene- ration in the direct cerebellar tract of the same side and the antero-lateral cerebellar tract of the opposite, which he, like Lowenthal and myself, traces to the vermis. I n the median sections of the cord the antero-lateral fibres are seen to consist of two distinct tracts, one the crossed afferent tract of Edinger, the other a crossed cere- bellar tract. I have shown that these tracts must arise from cells in the grey matter (perhaps at the base of the anterior horn), that they give off fibres which decussate in the anterior commissure; if they did not decussate then (like the direct cerebellar tract in the case in which the section was not in the mid-line, but involved the gray matter of one side), the degeneration of these two antero-lateral ascending tracts would not be equal and symmetrical on the two sides, but much more on the side in which the grey matter was de- stroyed. This inference is supported, moreover, by the experiments of Ehrlich and Brieger,10 and Singer11 and Miin- zer, viz., compression of the abdominal aorta in rabbits causes necrosis of the nerve cells in the lumbar spinal cord, and ascending degeneration in the antero-lateral ascending tract. I t has been inferred by the latter two observers that this tract arises from the cells of the grey matter of the lumbar region. Vide also a paper by A. S. Griinbaum,12 who con- firms the observations of Auerbach and Singer and Miinzer, but his observations are limited to the cord. H e considers as the result of his two experiments of Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OF THE MONKEY. 15 longitudinal division of the spinal cord in the cat that the anterior commissure fibres go in part to the antero-lateral column, and at the same time derive their origin from the grey matter of the opposite side. Schiifer25 has figured fibres of the antero-lateral tract going to the corpora quadrigemina after hemisection of the spinal cord in the monkey. TH E POSTERIOR COLUMN NUCLEI AND THE FILLET. A large and important literature exists upon the fillet based upon embryological and pathological data. For a full account, vide Flechsig and Hosel,15 Mahaim,10 Bruce,17 Dejerine,18 Von Monakow,19 but as my paper is solely an ex- perimental enquiry I shall only refer here especially to ex- perimental evidence upon the origin and course of the fibres arising from the posterior column nuclei. Von Vejas20 discovered that after destroying the posterior column nuclei in new born animals there occurred an atrophy of the internal arciform fibres of the same side, atrophy of the inter-olivary layer of the opposite side, and atrophy of the fillet, which could be followed up as high as the corpus trapezoides. Lastly, Singer and Miinzer,21 after experimental destruction of the nuclei of Burdach found atrophy of the internal arciform fibres, and a demonstrable atrophy of the fillet of the opposite side which could be followed up to the optic thalamus.* Monakow19 found after destruction of the parietal lobe in young animals atrophy of the fillet, of the internal arciform fibres of the opposite side, and of the nucleus gracilis of the opposite side. This, certainly, taken with the observations of Flechsig and Hosel upon a case of porencephalic defect of the central convolutions which was associated with atrophy of the fillet of the same side and of the internal arciform fibres and the posterior column nuclei of the oppo- site side, shows that the fillet may degenerate downwards * I am informed by Dr. Turner that, in conjunction with Professor Perrier their experiments showed that the fillet terminated in the optic thalamus. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 1 6 ORIGINAL ARTICLES AND CLINICAL CASES. and that the posterior column nuclei are in direct connec- tion (or indirect connection through the thalamus) with the central convolutions of the cortex. As I was unable to trace any degeneration beyond the optic thalamus, or to find any evidence of a degenerated cortical fillet, I should be inclined to agree with Mahaim and Monakow that the posterior column nuclei stand in connection with the optic thalamus by the fillet, and each portion of the thalamus is in relation to a definite part of the cortex, especially as he, Monakow, finds that the de- generation may proceed down to the posterior column nuclei leading to their atrophy and destruction; may not, therefore, the cells in the optic thalamus undergo a similar atrophy and disappearance ? The work of Flechsig and Hosel is, how- ever, of very great importance, because it shows that an affe- rent tract carrying sensory impulses from the periphery is in connection with what is called the " motor area," and which, therefore, cannot be purely motor. The internal arciform fibres form two groups, one coming from Goll's nucleus and decussating at a lower level, the other coming fromBurdach's nucleus. I am inclined to think, in contradistinction to Bechterew that the fibres proceeding from Goll's nucleus enter more into the formation of what is called the lateral fillet. I am of opinion that the distinction of different fillets is artificial, for it seems to me that the fibres of the so-called lateral fillet are fibres which are taking an oblique instead of a vertical direction. It is impossible to localise a lesion to Goll's nucleus, or to Burdach's nucleus alone, but I have formed this opinion from examination and com- parison of sections in which these two nuclei have been unequally injured, and by other facts which, if confirmed by further observations, would render the supposition that fibres issuing from Goll's nucleus enter into the formation of the lateral fillet still more probable. With regard to the degenerated fibres which descend the cord, many of which decussate in the anterior com- missure, it is very possible, as suggested by Ferrier and Turner, that these come from Deiter's nucleus which is in relation with the semi-circular canals by the external branch Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 PLATE II. POSTERIOR COLUMN NUCLEI LESIONS—PRODUCING DEGENERATION OF FILLET. l . 2. Lesions of medulla separating the posterior column nuclei from the arciform fibres issuing therefrom. (1) Lesion of nucleus gracilis showing the degenerated arciform fibres decussating to take up a position between the olive and pyramid. (2) Lesion higher up and separating Burdach's nucleus from the arciform fibres that issue from it. These degenerated fibres can be traced on the right hand side as the internal arciform fibres which sweep round behind the olive of the same side to reach the opposite interolivary layer. (8) Interolivary layer in the upper part of the medulla magnified about 80 diameters, composed of almost entirely black degenerated fibres, lying between the oliva and the pyramid. (4) Fillet above the lesion on the opposite side, and stained very black on account of the large number of degenerated fibres. Section from the upper part of pons varolii. P . W . JIOTT. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 PLATE II. A. Degeneration of fillet following lesions of posterior column nuclei. 5) Section of the pons at junction with crus cerebri magnified five diameters, (5) e degeneration of the fillet in the section is quite visible to the naked eye, Th but it is extremely difficult to photograph with such low magnification, but still it will be observed that the fillet is much blacker on one side than the other. (6) Section of optic thalamus showing degenerated fibres of fillet now taking a longitudinal and spreading course to end in the grey matter of this ganglion. P. W. UOTT. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OF THE MONKEY. 17 of the auditory nerve, and these fibres which degenerate downwards in the cord convey impulses from that nucleus connected with equilibration down to the anterior horn cells of the lumbo-sacral region, which of course in the monkey, like man, would preside over the muscles connected with movements and position in space. Certainly these fibres do not come directly from the cerebellum as Marchi22 sup- posed. This degeneration was extremely well marked in one case in which the lesion was extensive and involved Deiter's nucleus and other cranial nuclei, including the sixth (to the injury of which I attributed an upward degeneration in the posterior longitudinal bundle, of the opposite side mainly), extending as high as the third nucleus. These fibres may also possibly be ground fibres from motor cranial nuclei, particularly the ocular nuclei, and serving as bridges between spinal and cranial nuclei, in co-ordinate reflex movements directed by vision. Summary of results are shown in the three figs. 1, 2, 3, but- I shall briefly recapitulate the results of the fourteen experiments. (1) The column of Goll is formed especially by the fifth, sixth and seventh sub-thoracic roots. Section of the fourth sub-thoracic posterior root produced comparatively little degeneration of Goll's column (Experiment VII.), and further experiments which Dr. Sherrington and I have made show, as I anticipated, that few fibres enter into the formation of Goll's column above the fourth sub-thoracic. After uncomplicated unilateral section even of a large num- ber of roots, there is no degeneration in the opposite posterior column. The tract of Goll ends in the nucleus of the funi- culus gracilis. When this nucleus is destroyed, or the fibres issuing from it separated from the cells of the nucleus, a degeneration occurs in the internal arciform fibres, the opposite inter-olivary layer and fillet, which can be traced tip to the optic thalamus. It is impossible to injure Goll's nucleus without Burdach's nucleus being involved, and I found experimentally that the greater number of the fibres of the fillet come from the latter nucleus. In no case could degenerated fibres be traced to the cortex. VOL. XVIII. 2 Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 1 8 ORIGINAL ARTICLES AND CLINICAL CASES. (2) After unilateral section of roots in most instances degenerated fibres were found in the opposite antero-lateral column, but inasmuch as they were not always present in every case, I assume that these fibres come from cells of the grey matter of the same side as the lesion and cross over in the anterior commissure, and it is possible that cells from which, in all probability, these fibres arise are damaged by vascular changes in the grey matter—the result of the operation. These fibres form a tract internal to the ventral cerebellar tract, and in no case were the}' above forty in number even after section of eight posterior sub-thoracic roots. Some few degenerated fibres were observed in most cases in the lateral column of the same side ; none, how- ever, in the direct cerebellar tracts after section of roots below the second lumbar. In connection with this subject vide a preliminary com- munication by J. N. Langley 23 and H. K. Anderson. (3) After median section in the lumbar region for three- quarters of an inch, there was a symmetrical degeneration in the antero-lateral tract of the two sides. The fibres con- sist of two sets: (1) The ventral cerebellar, much the more numerous and situated most peripherally, which can be traced to the vermis, looping over the fifth nerve to reach the superior cerebellar peduncle, and then descending on its posterior aspect to the middle lobe of the cerebellum. (2) The crossed afferent tract of Gowers and Edinger (function unknown), which, in all probability, arises from cells of the grey matter, its fibres decussating in the anterior commis- sure. These fibres occupy exactly the same position, but are much more numerous than the small tract which was observed after unilateral section of roots. They can be traced right up the cord and the medulla in the pons varolii, above this lying to the outside of the lateral fillet, and ter- minating in the corpora quadrigemina, some few apparently extending to the optic thalamus. Ramon y Cajal24 has shown that fibres arise from cells at the base of the anterior horn, and decussate in the anterior commissure. It is, therefore, possible that these cells are the source of origin of these two ascending tracts. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 THE CENTRAL NERVOUS SYSTEM OP THE MONKEY. 19 In one case of median section the last dorsal segment was injured, and on the same side there was a very ex- tensive degeneration of the direct cerebellar tract. The fact that the ventral cerebellar tract is equal and symmetrical in these vertical -lesions whether the incision occupies the mid-line or not, shows that it, like the crossed afferent tract of Edinger, is a crossed cerebellar tract coming from the cells of the grey matter, possibly at the base of the anterior horn. REFERENCES. 1 MOTT. " The Bipolar Cells of the Spinal Cord and their connections," BRAIN, 1890. 2. SINGER, J. " Ueber secundiiro Degeneration in Riickenmarke des Hundes," Sitzimgsbcrichtc der Wiener Akacl., Bd. lxxxiv., Abth. iii., 3. LOWENTHAL. International iTonatschrift f. Anat. und Physiol., 1893, Bd. x. 4. ODDI et Rossi. " Sur les cours des voies afferentes de la moe'lle epiniere," Archives Ital. de Jiiol., xv., 1891. BERDEZ. "Recherches experimentales sur le trajet des fibres ccntri- petes dans la moiille epiniere," Iici-ue Mcd. de la Suisse Romandc, 0. EDINGER. " Einiges von Vevlauf der Gefiihlsbahnen in Centralen Nervensystems," Deutsche Hcd. Wochenschrift, 1890. C. MOTT. " Ascending Degenerations resulting from Lesions of the Spinal Cord in Monkeys," BBAIN, 1892. " Results of Hemisection of tlic Spinal Cord in Monkeys," Phil. Trans., B., 1891. 7. BECHTEREW. " Die sensiblun Bahuen irn Ruckenmark nach den Untersuchungen von Dr. P. Holzinger." 8. BHOWN-SKQUARD. " Remarques apropos des recherches du Dr. F. \V. Mott sur les effets de la section d'une moitie laterale de la mobile epiniere." 9. AxjEuiiACH, L. " Zur Auat. d. aufsteigenden degenerierenden Systeme des Riickcnmarks." Anat. Anzeiger, 1890. 10. EHRLICH andBniEGEH. " Ueber die Ausschaltung der Lendenmarks," Zcit.f. klin. Mcdicin, vii., 18S4. 11. SISGEB and M0NZP:K. " Beitrag. zur Anat. d. Centralnervensystems iusbesouders des Riickeninarkes," Wiener Dentschr., lvii., 1891. 12. ORCSBAUM, A. S. " Note on tlie I^egcnerations following Double Transverse Longitudinal and Anterior Coruual Lesions of the Spinal .Cord," Journal uf 1'hysiuloyn, May, 1894. 13. PEBRIER and TURNER. " Recent Work on the Cerebellum and its Relations, with Remarks on the Central Connections, &c," BBAIN, part i., 1894. Downloaded from http://brain.oxfordjournals.org/ by guest on June 7, 2016 2 0 OBIGINAL ARTICLES AND CLINICAL CASES. 14. RISIEN RUSSELL. " Denegerations consequent on Experimental Lesions of the Cerebellum," Brit. Med. Journ., Sept. 22, 1894. 15. FLECHSIG and HOSEL. " Die Central Windungen ein Central organ der Hinterstriinge," Archiv f. Psychiatrie, Bd. xxiv., Heft 8. 16. MAHAIM. "Ein Fall von Secundarer Erkrankung des Thalamus Opticus, &c," Archiv fiir Psychiatrie, Bd. xxv., Heft 2. 17. BBUCE. BEAIN, part lxiv., 1893. 18. DEJEBINE. Archiv de Physiologic, 1890. 19. MONAKOW. Neurol. Centralblatt, 1885, p. 65. 20. VON VEJAS. Archiv f. Psychiatrie, xvi., 1885. 21. SINGES. " Abth. d. math. nat. Klasse d. k.k. Akad. d. Wisseuschaft, Wien, 1890. 22. MABCHI. " Sulle degen consec. alia estirp. totale e parziale del cerveletto," Bit;. Spcr. di Frenatria, 1887. 23. <T. N. LANGLEY, F.E.S., and H. K. ANDEESON. "Notes on Degener- ation resulting from Section of Nerve Roots and Injury to the Spinal Cord," Proceedings of the Physiol. Soc, May 12,1894, Journal of Physiology, vol. xvi., June 5, 1894. 24. RAMON Y CAJAL. Croonian Lecture, March, 1894. 25. SCHAPEB. " Quain's Anatomy," vol. iii., part i., p. 33. 26. BOTTAEZI. Ueber die Hemisection des Riickenmarkes bei Hunden. Centralblatt fiir Physiologic, December 1, 1894.

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