38 SPECIAL SENSES. 



folds most multiplied are also those in which this sense is 

 most acute. 



111. No special apparatus for smell has yet been found 

 in Invertebrates. And yet there can be no doubt that in- 

 sects, crabs, and some mollusks perceive odors, since they 

 are attracted from a long distance by objects which diffuse 

 them. Some of them may be deceived by odors similar 

 to those of their prey ; which clearly shows that they are 

 led by this sense. 



4. Of Taste. 



112. TASTE is the sense by which the flavor of bodies is 

 perceived. It guides animals in the choice of their food, and 

 warns them to abstain from what is noxious. There is 

 also an intimate connection between the taste and the smell, 

 so that both these senses are called into requisition in 

 the selection of food. To perceive the flavor of a body, it 

 must come into immediate contact with the nerves of taste, 

 and hence these nerves are distributed at the entrance to 

 the digestive tube, on the surface of the tongue and the 

 palate. 



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 

 a particular 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 distributed. The extremities of the nerves gene- 

 rally terminate in little asperities of the surface, called papil- 

 la. Sometimes these papillse 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 

 beset with little stiff points ; sometimes fibrous and fringed 



