CUTANEOUS AND INTERNAL SENSATIONS 



1047 



the boundary as the stroking finger crosses it, coming from the 

 normal skin. This area is always much larger than the area in- 

 cluded in it, in which by quantitative methods e.g., the use of a 

 very fine camel's-hair brush, or more exactly by the v. Frey hairs 

 the sensibility to touch can be shown to be diminished (region of 

 hypoaesthesia to touch) (Fig. 443). 



For a variable distance within the ' stroking outline ' the hypo- 



<"V' '''' 



Fig. 444. Middle Cutaneous: Left Thigh (Trotter and Davies) (reduced by One- 

 third Linear). Twenty-six days after section. Results of examination with 

 v. Frey hairs. Touch spots marked responded to hair of 280 milligrammes' 

 pressure; those marked o to hair of 800 milligrammes; and those marked + to 

 hair of 2,280 milligrammes. The continuous line marks the limit within which 

 there was anaesthesia to the camel's-hair brush. 



aesthesia for tactile stimuli is so slight that it cannot be detected 

 with the brush or with cotton-wool, or even with the v. Frey hairs. 

 Like those of normal skin, 90 per cent, of its hair-bulbs respond to 

 a hair exerting a pressure of 70 milligrammes, and the remaining 

 10 per cent, to hairs exerting a pressure of 140 or 280 milligrammes. 

 Inside this zone of minimal hypoaesthesia the defect of sensibility 

 rapidly increases as we pass inwards, each line of hair bulb requiring 



