1046 



THE SENSES 



case the area of skin supplied by the nerve showed defects in seven 

 distinct functions: four sensory namely, sensibility to touch, cold, 

 heat, pain and three motor namely, vaso-motor, pilo-motor, 

 sudo-motor (sweat-secretory). The sensory changes showed a 

 central area of profound loss, an area of moderate extent surrounding 



STROKING ovriiM 



Fig. 443. Areas of Altered Sensibility produced by Section of all Three Branches 

 of the Internal Cutaneous Nerve of the Left Forearm (Trotter and Davies). 

 (Reduced by Two-thirds.) The thick lines show the areas of anaesthesia to the 

 brush. The thick continuous lines enclose the areas of the anterior and posterior 

 branches. The thick broken line and heavy shading mark the area of the in- 

 crease in anaesthesia which followed section of the middle branch. The thin 

 lines show the areas of minimal hypoaesthesia i.e., the ' stroking outlin'e.' The 

 complete oval outline is the ' stroking outline ' which followed section of the pos- 

 terior branch. The large addition to the oval on the right of the diagram shows the 

 increase in the ' stroking outline ' which followed section of the anterior branch. 

 The thin broken line and fine shading show the additions to the * stroking out- 

 line ' produced by division of the middle branch. 



this of partial loss, and a large area in which a qualitative change 

 could be alone dfetected.' The maximal extent of change, and 

 therefore the outer boundary of this third area, can be mapped out 

 by getting the subject to determine by light, stroking touches the 

 area which feels in any way unnatural when he touches it himself. 

 The most common feeling is that the skin has become smoother at 



