102' NERVOUS SYSTEM. 



diaphragm, and some muscles of the neck; they intercom- 

 municate chiefly so as to form plexuses, into which the 

 animal nerves send a few branches. 



Q. In any plexus do the animal nerves predominate? 



e/?. In the pulmonary the par vagum does. 



Q. How do you account for the innumerable interfac- 

 ings of the organic nerves? 



#. The filaments are not generally united in a trunk, 

 as the animal nerves are; the first run separately, not bound 

 in bundles. 



Q. What is remarkable in the course of the organic 

 nerves ? 



ft. They surround the arteries for some distance, like 

 a net-work. It is not so with the cerebral nerves, which 

 are in apposition only with the vessels. 



Q. What effects proceed from this reticular nervous en- 

 velope around the vessels? 



/?. The motion of the blood may have some effect on 

 the nerves. In support of this opinion it may be remark- 

 ed, that as nature has placed a great number of arteries at 

 the base of the brain, to agitate it with an alternate mo- 

 tion, she has also put the most considerable plexus of the 

 whole organic system upon one of the places to which the 

 red blood communicates the strongest impulse, viz. upon 

 the trunk of the coeliac artery. 



Q. What is the structure of the organic nerves? 



t/?. Some are in chords, like the animal; others are gray 

 or red filaments, and are very numerous. 



Q. What vital properties have these nerves? 



Jl. They have neither animal sensibility, nor sensible 

 organic contractility. They have organic sensibility, and 

 insensible organic contractility. 



