GENERAL ANATOMY OF THE NERVOUS SYSTEM. 321 



The Nervous system is the seat of intelligence, and also ex- 

 tends its physical influence to every part of the body. Both 

 the one and the other qualities reside in its central portion; the 

 first in the brain, and the second in the spinal marrow. When 

 the communication between the brain and the spinal marrow is 

 interrupted by an accident, or in an experiment, the difference 

 between the influence of the two is strongly marked:* the in- 

 fluence of the brain seeming to be entirely intellectual, so that 

 an animal will even bear its removal without immediate death; 

 while the influence of the spinal marrow is so indispensable to 

 life, that its destruction is followed by instantaneous and perfect 

 death.! Under common healthful circumstances, however, the 

 two seem to exercise a mixed influence on. all parts of the body; 

 as, for example, upon the reception of distressing intelligence, 

 the stomach ejects its contents, or refuses to receive more; 

 alarming intelligence causes the heart to flutter and to palpi- 

 tate, and both the bladder and the intestines to evacuate their 

 contents. On the contrary, a proper degree of corporeal ex- 

 ertion strengthens the intellectual operations, while its excess 

 debilitates them. That these several nervous influences are 

 seated in the central part of the nervous system, seems proved 

 by the fact, that where there has been a congenital deficiency 

 of all the limbs, or an accidental one, which, of course, removes 

 a very considerable portion of the peripheral part of the ner- 

 vous system, animal life and the intellectual operations have 

 still gone on vigorously. 



The following are some of the physical functions over which 

 the nervous system seems to preside. 



Digestion; the whole alimentary canal, from the mouth to the 

 anus, is under its influence : first, of all in mastication, then in 

 swallowing, afterwards in digestion and the absorption of chyle, 

 and, finally, in the passing of the effete matter out of the body. 

 It has been sufficiently proved, by the experiments of several 

 physiologists, that the section of the par vagum destroys the 

 faculty of digestion. 



Respiration; the mechanical act of this process, that by which 



* Legallois on the Principle of Life. 



f Observ. and Exper. on the Nervous System, by W. E. Homer. See Chap- 

 man's Med. and Phys. Journal, vol. i. p. 285. 



