344 COORDINATION AND SENSATION 



like those of touch, are limited almost entirely to the skin. 

 They are of two kinds, and are designated as heat sensa- 

 tions and as cold sensations. Whether the sense organs 

 for temperature are different from those of touch is not 

 known. It is known, however, that the same corpuscles 

 do not respond alike to heat, cold, and pressure. 



A Change of Temperature, rather than any specific degree 

 of heat or cold, is the active temperature stimulus. The 

 sensation of warmth is obtained when the temperature of 

 the skin is being raised, and of cold when it is being low- 

 ered. This explains why in going into a hallway from a 

 heated room one receives a sensation of cold, while in com- 

 ing into the same hallway from the outside air he receives 

 a sensation of warmth. It is for the same reason that we 

 are able to distinguish only the relative, not the actual, 

 temperature of bodies. 



Muscular Sensations. These are sensations produced 

 by impulses arising at the muscles. Such impulses origi- 

 nate at the fiber terminations which are found in both the 

 muscles and their tendons. By muscular sensations one is 

 conscious of the location of a contracting muscle and of 

 the degree of its tension. They also make it possible to 

 judge of the weight of objects. 



The Sensation of Taste. The sense organs of taste are 

 found chiefly in the mucous membrane covering the upper 

 surface of the tongue. Scattered over this surface are a 

 number of rounded elevations, or large papillae (A, Fig. 

 146). Toward the back of the tongue two rows of these, 

 larger than the others, converge to meet at an angle, where 

 is located a papilla of exceptional size. Surrounding each 

 papilla is a narrow depression, within which are found the 

 sense organs of taste (B, Fig. 146). These are called, from 

 their shape, taste buds, and each bud contains a central 



