980 A MANUAL OF PHYSIOLOGY 



a local compensatory mechanism, and not upon regeneration of 

 the vaso-motor fibres. Recovery of all the functions dependent 

 upon regeneration begins about the same time, and this recovery 

 progresses over the area at about the same rate for all, although 

 the rate at which they progress towards normal acuity is dif- 

 ferent. 



Sensibility to touch probably appears a little earlier than sensi- 

 bility to cold and pain. Yet the recovery of touch does not 

 progress so fast, and for a while a given zone of the recovering 

 area remains hypoaesthetic (less sensitive than normal) to touch, 

 while to cold and pain it soon becomes even hypersensitive. 

 The most remarkable peculiarities of a recovering area are : 

 (i) This qualitative change, in virtue of which cold, pain, and 

 the pain element of heat are intensified, while touch is little 

 altered, although more difficult to elicit ; (2) the reference of 

 sensations, not to the point stimulated, but to distant parts of 

 the area. 



' When a spot which has developed this peripheral reference is 

 touched, one of two possibilities may occur : either the touch is 

 felt locally, and is referred as well, or nothing is felt locally, and 

 the touch is felt in the area of peripheral reference. The region 

 in which the referred touch is felt is always at the edge of the 

 most peripheral part of the anaesthesia,' perhaps more than 

 a foot away from the spot actually touched. The peripheral 

 reference of cold is even more striking, particularly in the re- 

 markable intensity of the referred sensation. 



Peripheral reference occurs also with pain. ' The referred 

 pain shows three well-marked qualities : it is, proportionately 

 to the stimulus, very intense ; it does not reproduce a normal 

 sensation with the exactitude found in the case of touch or 

 cold, but has a special quality of strangeness and unpleasantness, 

 such as no pin-prick on normal skin can give ; finally, it produces 

 an almost irresistible desire on the part of the subject to rub or 

 scratch the region in which it is felt.' As recovery proceeds 

 the local sensory response becomes more distinct, and the 

 abnormal quality of both local and referred sensations fades. 

 But ' while peripheral reference is the earliest phenomenon of 

 recovery, it persists until recovery is so far advanced that hypo- 

 aesthesia is scarcely detectable by any quantitative methods.' 



It is a remarkable circumstance that during regeneration 

 stimulation of the nerve-trunk itself below the section, by the 

 application of touch, cold, or pain stimuli to the skin over its 

 course, produces peripherally referred sensations of the corre- 

 sponding kind. This is the case even when the nerve is stimu- 

 lated outside the formerly anaesthetic area, and suggests that the 

 nerve-trunk itself has acquired the specific sensibility normally 



