THE SPECIAL SENSES 229 



In mammals taste organs are situated on certain parts of 

 the tongue, and have the form of rather large, low, broad 

 papillae,- each bearing many small taste-buds (Fig. 142). 

 In fishes similar papillae and buds have been found in vari- 

 ous places on the sur- 

 face of the body, from 

 which it is believed that 

 the sense of taste in 

 fishes is not limited to 

 the mouth. In insects 

 the taste - papillae and 

 taste -pits are grouped 



in certain places On the FIG. 142.-Vertical section of large papilla on 

 mOUth parts, being eS- ^ f a Calf ; * taste-buds. -After 



pecially abundant on 



the tips of small, segmented, feeler-like processes called 

 palpi, which project from the under lip and from the so- 

 called maxillae. 



121. The sense of smelL Smelling and tasting are closely 

 allied, the one testing substances dissolved, the other test- 

 ing substances vaporized. The organs of the sense of 

 smell are, like those of taste, simple nerve-endings in papil- 

 lae or pits. The substance to be smelled must, however, 

 be in a very finely divided form ; it must come to the or- 

 gans of smell as a gas or vapor, and not, as to the organs of 

 taste, in liquid condition. The organs of smell are situated 

 usually on the head, but as the sense of smell is used not 

 alone for the testing of food, but for many other purposes, 

 the organs of smell are not, like those of taste, situated 

 principally in or near the mouth. Smell is a special sense 

 of much wider range of use than taste. By smell animals 

 can discover food, avoid enemies, and find their mates. 

 They can test the air they breathe as well as the food they 

 eat. In the matter of the testing of food the senses of 

 both taste and smell are constantly used, and are indeed 

 intimately associated. 

 16 



