n 



though tlie nervous fibrils in each packet 

 appear distinct, and may be separated from 

 each other in the manner already described, 

 yet they have nevertheless transverse com- 

 munications with each other. Each 

 nervous fibre has been supposed to be 

 covered by investing membranes similar 

 to those of the brain ; but this opinion is 

 founded on an analogy with what is observed 

 in the optic nerve, rather than on ac- 

 tual observation with respect to 4 other-. 

 That they have investing membranes is 

 clear, and ;we are told that we may dib- 

 solve the medullary or n&fvous matter 

 by an alkali, and leave these investing 

 membranes ; or on the other hand, that we 

 iilay dissolve the investiag membratea 

 by nitric acid, and leavte /the medullary 

 fibres. 



Having thus spoken of the chief cir- 

 cumstances relating to the anatomy of 



