158 



ANIMALS 



of the body, more particularly in the region of the mouth, but 

 with this exception we can say that for all vertebrates the organs 

 of taste and of smell are limited to the surface of the cavities 

 of the mouth and nostrils, respectively. 



371. The organs of taste are called taste buds, because the 

 sense cells are grouped in small cask-shaped clusters. The taste 



buds may occur in various 

 parts of the mouth, but in 

 mammals they are chiefly 

 found on the sides of the 

 fungiform and circumvallate 

 papillae (and the foHate 

 papillae, where they are 

 found) of the tongue. The 

 bud consists of two kinds of 

 cells, both very much elon- 

 gated. One of these, the 

 supporting cells, taper to a 

 point at the free end while 

 the deeper end is very irregu- 

 lar in outline. The sensory 

 cells are more slender and end 

 at the free extremity in a short cuticular hair. At the other 

 end they broaden out into a slight enlargement. They have 

 no fibre processes. Nerve fibres from deeper lying nerve cells 

 form a network of numerous branches, which enclose the bud 

 and penetrate between the cells which compose it. 



372. In man there are four kinds of taste sensations: sweet, 

 sour, salt and bitter. At the tip of the tongue sweet is most 

 readily detected, sour along the edges, salt at the tip and edges, 

 and bitter at the base of the tongue. We conclude, therefore, 

 that these four sensations are yielded by as many different 

 kinds of organs which, however, are not distinguishable 

 anatomically. 



Fig, 78. — Antennae of a moth, Samia 

 cecropia. A, Of male; B, of female. 

 (From Folsom.) 



