Release of Function in the Nervous System. 189 



the response to those which remained might become peculiarly vivid. 

 Eeaction to a prick was abnormal and excessive ; the patient complained that 

 it was more painful, although measurements showed that sensibility to this 

 form of stimulation was not increased. 



When such a nerve as the median or ulnar is divided, the extent of the 

 insensibility to pricking is usually less than that of the anaesthesia to light 

 touch (see figs. 2 and 3). Some fourteen days or more after the injury, this 

 intermediate zone begins to behave in a peculiar manner. If the point of 

 a pin is dragged across the skin from normal to affected parts, it is said to 

 be " more painful " or to " hurt more " as it passes over the portion of the 

 palm sensitive to pricking, but not to the lighter forms of tactile stimu- 

 lation. This would usually be spoken of as " hyperalgesia " ; but measure- 

 ments have shown that the threshold is raised to cutaneous painful stimuli, 

 and that, although the response is excessive, this area is in reality one of 

 diminished sensibility. 



The phenomena exhibited by a part of the skin, sensitive to pain, heat and cold, 

 but deprived of some of the higher elements of sensibility, could be worked out 

 in greater detail during the course of the experiment on my arm. Within a 

 little over six weeks, after division and reunion of my radial and external 

 cutaneous nerves, sensibility began to return ; seven months after the opera- 

 tion, the back of the hand was sensitive to pain, to cold, to heat and to any 

 form of contact which moved the hairs. But the sensation experienced was 

 peculiar and quite unlike any reaction from normal parts ; for, although less 

 easily evoked, it was unduly vivid. The pain of a prick was intolerable ; cold 

 was said to be colder, and a suitable warm stimulus produced a more actively 

 pleasant effect than over the normal skin ; during this stage of recovery a high 

 threshold was associated with a brisker response ([9], p. 258, et seq.). 



The sensation aroused within the affected area had certain other peculiar 

 characteristics. It radiated widely and was not confined to the neighbour- 

 hood of the stimulated spot. Portions of the affected area seemed to be 

 linked up together, so that stimulation of the one evoked a sensation of 

 the same specific quality referred to the other. Thus, brushing the hairs, 

 pricking, or the application of heat and cold to the neighbourhood of the 

 index knuckle, caused a diffuse outburst of the appropriate sensation over 

 the dorsal aspect of the thumb. Moreover, the response was massive, 

 diffuse, and bore little relation to the measured strength of the stimulus, 

 provided it was effective ([9], p. 297). 



Trotter and Davies ([18], p. 121), who divided seven nerve trunks in 

 different parts of their bodies, write as follows of these peculiar manifesta- 

 tions : — " In addition to their directly practical importance, intensification 



