THE SENSES 



ties. The localization of the sensations and the power of discrimi- 

 nating two points were also investigated. 



The general tendency during recovery was from anaesthesia or 

 hypoaesthesia through decreasing degrees of hypoaesthesia to normal. 

 Warmth and cold, however, passed from hypoaesthesia through a 

 stage of hyperaesthesia on their way to normal. Pain, pressure, and 

 cold approached normality at about the same rate, but in compari- 

 son with these the return of warmth sensation was much delayed 



Fig. 466. Volar Aspect of Left Forearm, showing Affected Region in Outline. 

 The larger area was that marked off by the subject with the camel's hair 

 brush as insensitive. The inclosed smaller area is that which was marked off 

 when the experimenter manipulated the brush, and the subject with closed 

 eyes reported when he felt anything at all. This smaller area was taken as 

 the region of greatest change in sensitivity, and the experiments on localization 

 and the discrimination of two points were mainly made within this area. The 

 dotted line shows the approximate course of the nerve, divided at S. The 

 horizontal and vertical lines dividing the area into small squares were impressed 

 by a rubber stamp on the skin, to facilitate identification of points. The 

 position of each point stimulated was fixed with reference to these rectilinear 

 co-ordinates, the tattooed point represented by the Maltese cross being taken 

 as the origin, and the distances in mm. measured in the central (C), peri- 

 pheral (P), radial (R), and ulnar (U) directions (Boring). 



For all four the distribution of sensitivity over the skin was irregular 

 and patchy, and no definite boundaries could be drawn. In general, 

 however, immediately after division of the nerve the central zone 

 of the affected area was practi _:ally anaesthetic as regards cutaneous 

 sensation. This was surrounded by a zone of decreased sensitivity. 

 In the return of sensibility the outer zone preceded the inner. 

 No new modes or qualities of sensation were observed at any time, 

 although ' a number of unusual sensory complexes, which might be 

 described by an untrained observer as new sensations, were noted. 



