THE STRUCTURAL AND FUNCTIONAL SYSTEMS 



67 



In addition, there are the autonomic nerves, of which the sympa- 

 thetic nerves (Fig. 37) are a part, and which connect with both 

 cranial and spinal nerves. These innervate the blood vessels and 

 viscera. 



The relative development of the nervous system of vertebrate 

 animals, particularly of the brain, may be mentioned here. If 



A.7ISH 



r.BIBD 



Fig. 39. — Brains of representative vertebrates from dorsal view {cf. the 

 lateral views shown in P'ig. 288, p. 532). 



cbl, cerebellum; cbm, cerebrum; dien, diencephalon ; jtid, medulla oblongata; ol.L, 

 olfactory lobe; op.l., optic lobe. 



one examines tTie brains of a fish, an amphibian, a reptile, a bird 

 and a mammal (Fig. 39), one sees that the cerebrum exhibits a 

 progressive increase in size and complexity in passing from the 

 lower to the higher types. The intelligence of the animals in 

 question may likewise be arranged in an order that parallels 



