NERVOUS SYSTEM. 85 



nerves from their connexion or junction with the brain, 

 to their exit from the bony canal. The pia mater con- 

 tinues on the nerves. 



Q. How do the tunics of the optic nerve differ from 

 those of other nerves? 



Ji. It has a fibrous investment from its origin to the 

 sclerotic coat. 



Q.- What nerves converge after their origin? 



*ft. The olfactory; all the rest remain separate. 



Q. What nerves go to their destination without com- 

 municating with other nerves ? 



ft. The olfactory, the optic and auditory. 



Q. Do the nerves of the spine make their egress imme- 

 diately opposite their origin ? 



#. They do not; the lower or lumbar run several 

 inches in the spinal canal before they leave it. 



Q. Of what practical import is this fact? 



ft. In order that moxa should be applied at the origin 

 of the nerves, the immediate exit of the cervical from the 

 spine, and the long course within the spinal column which 

 the lumbar pursue before their exit, should be well known. 



Q. How are the plexuses of the spinal nerves formed ? 



#. By each nerve sending a branch to the one above 

 and below it. 



Q. How do you best understand the distribution of the 

 spinal nerves? 



Jl. By taking them as they arise from the plexuses and 

 not regarding them as pairs of nerves. 



Q. Are the plexuses confined to those at the exit of the 

 nerve ? 



*fl. No other communicating chords form as the nerves 

 proceed in their course. 



