174 



NERVOUS SYSTEM OF VERTEBRATES. 



frequently special organs such as the barblets about the mouth, 

 or the fins, are richly provided with taste buds and are dragged 

 about on the bottom or otherwise used in the active search for food. 

 In short, the function of the taste organs of fish-like vertebrates 

 is to detect food and to discover its location. In terrestrial animals, 

 on the other hand, the taste organs in the mouth can rarely be 

 used in the search for food. Their only service is to test the 

 food after it is taken into the mouth to discover if it is desirable 

 to eat. Terrestrial vertebrates depend chiefly on the senses of 

 smell and sight for finding food. This explains the relatively 



IX Xll sp.vl 



Sec. gustatory tract 



Tr. mammillo-bulbaris 



Fig. 92. — A diagram representing the centers and tracts related to the visceral 

 sensory components m fishes. 



slight importance of the sense of taste and the small size of its 

 apparatus in higher vertebrates. At the same time, in higher 

 vertebrates the general visceral system has been reduced in the 

 head by the loss of the gills and more highly developed in the 

 trunk in connection with the sympathetic system. 



A comparison of the diagram for the \dsceral and gustatory 

 apparatus with those for the general and special cutaneous appa- 

 ratus will show how widely these di^dsions of the nervous system 

 differ from one another. The student should now turn to the 

 tabular definition of the two divisions (on p. loi) and review this in 

 connection with the figures in this and previous chapters. 



