62 SPECIAL SENSES. 



111. No special apparatus for smell has yet been found in 

 Invertebrates. And yet there can be no doubt that insects, 

 crabs, and some mollusks perceive odors, since they are 

 attracted from a long distance by the odor of objects. Some 

 of these animals may be deceived by odors s'milar to those 

 of their prey ; which clearly shows that they are led to it by 

 this sense. The carrion fly will deposit its eggs on plants 

 which have the smell of tainted flesh. 



4. Of Taste. 



112. Taste is the sense by which the flavor of bodies ig 

 perceived. That the flavor of a body may be perceived, it 

 must come into immediate contact with the nerves of taste ; 

 these nerves are distributed at the entrance to the digestive 

 tube, on the surface of the tongue and the palate. By this 

 sense, animals are guided in the choice of their food, and 

 warned to abstain from what is noxious. There is an inti- 

 mate connection between the taste and the smell, so that 

 both these senses are called into requisition in the selection 

 of food. 



113. The nerves of taste are not so strictly special as 

 those of sight and hearing. They do not proceed from one 

 single trunk, and, in the embryo, do not correspond to an 

 isolated part of the brain. The tongue, in particular, receives 

 nerves from several trunks ; and taste is perfect in proportion 

 as the nerves which go to the tongue are more minutely dis- 

 tributed. The extremities of the nerves generally terminate 

 in little asperities of the surface, called papillcE. Sometimes 

 these papillae are very harsh, as in the cat and the ox ; and 

 again they are very delicate, as in the human tongue, in that 

 of the dog, horse, &c. 



114. Birds have the tongue cartilaginous, sometimes be- 

 set with little stiff* points ; sometimes fibrous or fringed 

 lit the edges. In the parrots, it is thick and fleshy; 



