346 



COORDINATION AND SENSATION 



The different taste sensations are described as bitter, 

 sweet, sour, and saline, and in the order named are recog- 

 nized as the tastes of quinine, sugar, vinegar, and salt. As 

 to how these different tastes are produced, little is known. 

 Flavors such as vanilla and lemon, and the flavors of meats 

 and fruits, are really smelled and not tasted. Taste serves 

 two main purposes : it is an aid in the selection of food and it 

 is a means of stimulating the digestive, glands (page 161). 



The Sensation of Smell. The sense organs of smell 

 are found in the mucous membrane lining the upper divi- 

 sions of the nasal cavities. Here are found two kinds of 



4 



Olfactory 

 bulb 



A B 



FIG. 147. Sense organ of smell. A. Distribution of nerves in outer 

 wall of nasal cavity. I. Turbinated bones. 2. Branch of fifth pair of nerves. 

 3. Branches of olfactory nerve. 4. Olfactory bulb. B. Diagram showing 

 connection of neurons concerned in smell. 



cells in great abundance column-shaped epithelial cells 

 and the cells which are recognized as the sense organs of 

 smell. These olfactory cells are spindle-shaped, having at 

 one end a slender, thread-like projection which reaches 

 the surface, and at the other end a fiber which joins an 

 olfactory nerve (B, Fig. 147). In fact, the olfactory cells 



