CHAPTER I. 



THE SPINAL CORD. 



SEC. 1. ON SOME FEATURES OF THE SPINAL NERVES. 



558. WE have called the muscular and nervous tissues the 

 master tissues of the body ; but a special part of the nervous 

 system, that which we know as the central nervous system, the 

 brain and spinal cord, is supreme among the nervous tissues and 

 is master of the skeletal muscles as well as of the rest of the 

 body. We have already (Book I. Chap, ill.) touched on some of 

 the general features of the nervous system, and have now to study 

 in detail the working of the brain and spinal cord. We have to 

 inquire what we know concerning the laws which regulate the 

 discharge of efferent impulses from the brain or from the cord, 

 and to learn how that discharge is determined on the one hand 

 by intrinsic changes originating, apparently, in the substance of 

 the brain or of the cord, and on the other hand by the nature and 

 amount of the afferent impulses which reach them along afferent 

 nerves. 



As we shall see the study of the spinal cord cannot be wholly 

 separated from that of the brain, the two being very closely related. 

 Nevertheless it will be of advantage to deal with the spinal cord 

 by itself as far as we can. The medulla oblongata or spinal 

 bulb 1 we shall consider as part of the brain. But before we speak 



1 The term medulla oblongata is not only long, but presents difficulties, 

 since the word medulla is now rarely used to denote the whole spinal cord (medulla 

 spinalis) but is generally used to denote the peculiar coat of a nerve fibre, the 

 white substance of Schwann. In using instead the word bulb or if necessary, 

 spinal bulb there is little fear of confusion with any other kind of bulb. The 

 adjective is in not uncommon use, in such phrases as 'bulbar paralysis.' 



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