490 STUDIES IN ADVANCED PHYSIOLOGY. 



upper ends of the sticks somewhat pointed and projecting 

 above the body of the barrel free into the exterior. These 

 taste bulbs are most plentiful in the circular depressions 

 around the circumvallate papillae and the free ends of the 

 sensory cells project into this groove . They are also found, 

 although not so plentifully, on the fungiform papillae and 

 even on the soft palate and epiglottis. Their preponderance 

 towards the back of the tongue and mouth explains the 

 common experience that the sense of taste is most acute in 

 those regions. In fact, the sense of taste is rather imperfect 

 at the tip of the tongue. Yet the tip seems best adapted for 

 sour sensations but not so well for bitter sensations. The 

 acuteness of the sensation in the back of the mouth possibly 

 finds its explanation in the tendency which this gives to the 

 animal to swallow its food. 



The anatomical arrangements for the perception of taste 

 at the tip of the tongue are quite different from the taste 

 bulbs, the sensory nerves here ending merely in fine net- 

 works of fibrils. In the description of the cranial nerves 

 in the preceding chapter the glossopharyngeal was pointed 

 out as the main nerve of taste, while the taste sensations 

 from the tip of the tongue were ascribed to the trigeminal. 

 Some physiologists have tried to make the difference in the 

 nerves going to these areas explain the difference in the 

 acuteness of the sensation, but more recent work seems to 

 show that even the fibers that go to the tip of the tongue 

 are derived from the glossopharyngeal nerve which reach 

 the tip of the tongue along the trunk of the trigeminal 

 nerve. 



THE NATURE OF A TASTE SENSATION. 



Gustatory sensations are produced by substances, either 

 in solution when introduced into the mouth, or dissolved by 

 the liquids in the mouth. Gases dissolved in the liquids of 

 the mouth may thus give rise to actual tastes. In what 

 manner these substances act upon the nerve endings to 

 produce the sensations of sweet, or sour, or salty, etc., is 

 entirely unknown. We are at present entirely unable to 



