THE TEMPERATURE-SENSES 



365 



tions) a single isolated afferent end-organ of any sort, because of its 

 smallness and transparency. 



FIG. 216 



The nerve-endings of Ruffini ("plume-organs") from the subcutaneous tissue of the finger. 

 They have strong connective-tissue sheaths and the varicosities end in knoblets. (Ruffini.) 

 Perhaps the end-organs for heat. 



FIG. 217 



Two maps showing the topography of the temperature-sensations. Each square represents a 

 square inch of the back of the left hands of two men. Axis of the hand was from left to right. 

 The heat-spots are vertically shaded, the cold-spots horizontally, while the dotted areas repre- 

 sent tactile sensibility. The tactile spot a is 0.01 sq. in., the heat-spot 6 is 0.02 sq. in. (Hall.) 



The nerves of the thermic organs have not been isolated from the 

 afferent trunks going into the cord by the posterior routes. There is 

 good evidence, however, that each of these senses of heat and cold has 



