HO IV ANIMALS KNOIV THINGS 



i°5 



into actual contact with it. The taste organs (fig. 71) 

 of man and the other air-breathing animals are located 

 in the mouth or on the mouth parts. It is also necessary 

 that the food substance to be tasted be dissolved. This 

 is accomplished by the fluids poured into the mouth from 

 the salivary glands. With the lower aquatic animals it 

 is not improbable that taste organs are situated on other 

 parts of the body besides the mouth, and that taste is 



Fig. 70. Fig. 71. 



Fig. 70. — Tactile (touch) corpuscle of the skin of man; n, nerve. (Greatly 



magnified ; after Kolliker. ) 

 Fig. 71. — Papilla with taste buds (t.b) from tongue of a calf (Greatly 



magnitied; after Loven.) 



used not only to test food substances but also the chem- 

 ical character of the fluid medium in which they live. 



Smelling and tasting are closely allied, the one testing 

 substances dissolved, the other substances vaporized. 

 The organs of the sense of smell are, like those of taste, 

 simple nerve-endings in papilla; or pits. By smell ani- 

 mals can discover food, avoid enemies, and find their 

 mates. With the strictly aquatic animals the sense of 

 smell is probably but little developed. There is little 

 opportunity for a gas or vapor to reach them, and only 

 as gas or vapor can a substance be smelled. With 

 these animals the sense of taste must take the place 

 of the olfactory sense. But among the insects, mostly 

 terrestrial animals, there is an extraordinary develop- 

 ment of the sense of smell. It is indeed probably 

 their principal special sense. Insects must depend on 



