Release of Function in the Nervous System. 193 



areas which have lost the more discriminative aspects of tactile sensibility. 

 The cutaneous fibres of the ulnar nerve, which conduct painful impressions, 

 extend into the " median area " on the radial half of the palm. In a similar 

 manner, a varying portion of the so-called " ulnar area" is innervated by 

 fibres from the median. The supply of these two nerves overlaps con- 



FiG. 1. Fig. 2. Fig, 3. 



Fig. 1.- — To show the efifecfc produced by surgical division of the ulnar nerve. (From 

 the same patient as fig. 3 ; the tenderness has disappeared.) The black area 

 corresponds to the complete cutaneous analgesia. The dotted area represents the 

 parts in a condition of protopathic sensibility ; the surface was insensitive to the 

 lighter degrees of contact, such as cotton-wool, and two points of the compasses 

 could not be discriminated within normal limits. If a pin was dragged lightly 

 across the palm from normal to abnormal parts it was said to " hurt more " when 

 it passed to the ulnar side of this border. 



Fig. 2. — To show the extent of the changes in cutaneous sensibility which may follow 

 division of the median nerve. The black area corresponds to the complete cutaneous 

 analgesia. An example has been chosen where the extent of this total loss was 

 comparatively small. The dotted area represents the parts in a condition of 

 protopathic sensibility ; this does not extend beyond the limits of the loss to the 

 lighter degrees of tactile stimulation. 



Fig. 3." — To show the extent of the superficial tenderness on the palmar aspect of the 

 hand, due to irritation of the ulnar nerve caused by a bullet wound of the forearm 

 (Head and Sherren[9], p. 210, et seq.). The limits of this tenderness could not be 

 defined exactly as it merged into parts that responded normally to the point of 

 a pin dragged lightly across the surface. All tenderness disappeared after division 

 of ulnar nerve (c/. fig. 1). 



siderably as far as painful sensibility is concerned. But the extent of the 

 over-reaction, which may follow division of one or other of these peripheral 

 nerves, is strictly limited to the borders of loss to the lighter degrees of 

 tactile stimulation; it does not spread beyond them on to those parts of the 

 VOL. xcii. — B. Q 



