OF THE NERVOUS SYSTEM. 



379 



parts of which are connected by transverse and longitudinal com- 

 missures. Its ganglia occupy the cavities of the cranium and the 

 spinal canal, and send out their nerves through openings in the 

 bony walls of these cavities. 



The other portion of the nervous system of vertebrata is that 

 which presides over the functions of vegetative life. It is called 

 the ganglionic or great sympathetic system. Its ganglia are situated 

 anteriorly to the spinal column, in the visceral cavities of the body, 

 and are connected, like the others, by transverse and longitudinal 

 commissures. This part of the nervous system is symmetrical in 

 the neck and thorax, but is uusymmetrical in the abdomen, where 

 it attains its largest size and its most complete development. 



The vertebrate animals, as a general rule, are very much superior 

 to the other classes, in intelligence and activity, as well as in the 

 variety and complicated character of their motions; while their 

 nutritive or vegetative functions, 

 on the other hand, are not particu- Fig. 126. 



larly well developed. Accordingly 

 we find that in these animals the 

 cerebro-spinal system of nerves 

 preponderates very much, in im- 

 portance and extent, over that of 

 the great sympathetic. The quan- 

 tity of nervous matter contained 

 in the brain and spinal cord is, 

 even in the lowest vertebrate ani- 

 mal, very much greater than that 

 contained in the system of the great 

 sympathetic; and this preponder- 

 ance increases, in the higher classes, 

 just in proportion to their supe- 

 riority in intelligence, sensation, 

 power of motion, and other func- 

 tions of a purely animal character. 



The spinal cord is very nearly 

 alike in the different classes of ver- 

 tebrate animals. It is a nearly 

 cylindrical cord, running from one 

 end of the spinal canal ito the other, 

 and connected at its anterior ex- 

 tremity with the ganglia of the brain. (Fig. 126.) It is divided, 



CEREBRO-SiMXAL STSTEM OF MAX. 



1. Cerebrum. 2. Cereb Hum. 3,3,3. Spin d 

 cord and nerves. 4, 4. Brachial nerves. 

 5, 5. Sacral nerves. 



