388 



COMPARATIVE ZOOLOGY 



hoofed animals. The elephant and parrot are remark- 

 ably intelligent, and are as celebrated for their tactual 

 power. 



Taste is more refined than touch, since it gives a 

 knowledge of properties which can not be felt. It is 

 always placed at the entrance to the digestive canal, 

 as its chief purpose is to guide animals in their choice 

 of food. Special organs of taste have been detected in 

 only a few of the invertebrates, though all seem to 

 exercise a faculty in selecting their food. Even in fishes, 

 amphibians, reptiles, and birds this sense is very obtuse, 

 for they bolt their food. But the higher vertebrates 

 have it well developed. If is confined to the tongue, 

 and is most delicate at the root. 144 A state of solution 

 and an actual contact of the fluid are necessary condi- 

 tions. 



Smell is the perception of odors, i.e., certain substances 

 in the gaseous or volatile state. Many invertebrates have 

 this sense : snails, e.g., seem to be guided to their food 

 by its scent, and flies soon find a 

 piece of meat. In the latter the 

 organ is probably located on the 

 antennae. In vertebrates, it is placed 

 at the entrance to the respiratory 

 tube, in the upper region of the nose. 

 There the olfactory nerves/which 

 cavit y- issue from the olfactory lobe of the 



brain, and pass through the ethmoid bone, or roof of the 

 nasal cavity, are distributed over a moist mucous mem- 

 brane. The odorous substance, in a gaseous or finely 

 divided state, is dissolved in the mucus covering this 

 membrane. In fishes and reptiles generally, this organ 

 is feebly developed ; sharks, however, gather from a 

 great distance around a carcass. In the porpoises< and 

 whales it is nearly or entirely wanting. Among birds, 



