to 48 



THE SENSES 



a heavier pressure than the line external to it, till at last 3 J or 

 4 grammes' pressure is needed to cause a sensation of touch and 

 inside of this line of hairs the skin does not respond at all. When 

 a bristle of this pressure fails to elicit touch sensation, no greater 

 pressure will in general do so (Fig. 444). 



For thermal sensibility there is also a region of complete anses- 

 thesia and a region of partial anaesthesia. The best way of out- 



":: I* 



\ : ..'... | :t : : :'.: : ; : l : :!: 



Fig. 445. Middle Cutaneous: Left Thigh (Trotter and Davies). Twenty-one days 

 after section. Results of examination with temperature of o C. On spots 

 marked stimulus was felt as cold; on spots marked o it was felt as cool. The 

 blank area is that of thermal anaesthesia. The continuous outline marks the 

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



lining these is the use of a temperature of o C. as the stimulus 

 (Fig- 445)- 



Outside the zone of complete thermal anaesthesia there is a region 

 in wjiich temperature sensations are distinctly elicited, but do not 

 possess the normal intensity, the temperature of o C., for example, 

 being felt only as cool, and not as cold. The outer limit of this 

 region is the line at which the temperature of o C. is first felt as 



