DISSOCIATION OF COLD AND WARM SENSIBILITY DURING COMPRESSION OF THE UPPER LIMB
AbstractINTRODUCTION THE occurrence of sensory dissociation in experimental nerve blocks has often been used as evidence supporting the theory that cutaneous sensation is founded upon four basic "modalities"âtouch, pain, cold and warmâeach of which has its distinct anatomical apparatus. In particular, the order in which these forms of sensibility fail in such blocks has been compared with the order.in which groups of fibres tend to fall out according to their size when an animal nerve is blocked in vitro. These comparisons involve many difficulties, among which are the contradictory results obtained in relation to cold and warm sensibility (Sinclair, 1955). One of the chief factors in determining the order of sensory loss in a human experiment is the relative intensity of the various stimuli used, and in none of the work on sensory dissociation has an attempt been made to use standardized thermal stimuli. We therefore considered that further work might provide some more consistent information regarding the modalities of cold and warm. Compression blocks were used since these yield a more stable order of sensory loss than procaine blocks, and are not complicated by thermal disturbances such as occur in cold blocks (Sinclair and Hinshaw, 19506, 1951a).