554 COURSE OF THE NERVOUS FIBRES. 



base of the brain, and go to increase its bulk. On the other 

 hand, recent researches have shown that a part only of the 

 nerves, are continuous with the brain ; some terminating and some 

 originating in the gangha as organic filaments, and others termi- 

 nating and originating in the cineritious substance of the spinal 

 marrow and the base of the brain, to which the term excito^ 

 motory has been applied. The anatomical grounds for the adop- 

 tion of this term require to be investigated. That it renders the 

 'study of the functions of the nervous system, more clear and 

 comprehensible, is something in proof of its anatomical correct- 

 ness. The researches of Flourens* have shown, conclusively, 

 that the seat of ordinary sensation and voluntary motion, is ex- 

 clusively in the brain, and that yet there are many parts of the 

 body gifted with peculiar instinctive sensations and involuntary 

 movements, which are capable of exercising their offices to a 

 greater or less extent, even when separated from the brain. 

 Such are the parts which receive their supply from the ganglia 

 of the sympathetic, and some too which obtain it through nerves 

 sent off from the spinal marrow and medulla oblongata. 

 The dissections and experiments of Sir C. Bell, before 

 whose time the spinal marrow was considered a sort of 

 tail-like appendage to the brain, as well as those of Magendie, 

 have established as unquestioned facts, that the anterior and 

 posterior roots of the spinal nerves, and the anterior and pos- 

 terior colunms of the spinal marrow from which these roots 

 come out, are destined, — the former or anterior, for motion, 

 and the latter or posterior, for sensation. Many of the other 

 opinions of Sir C. Bell, in relation to the nervous system, 

 have not stood the test of closer examination, and according 

 to Mr. Grainger, his own views in regard to them were altered. 

 Thus, beside the anterior and posterior columns of each half 

 of the spinal marrow he admitted a middle or lateral portion, 

 between them, which other anatomists have not been able to 

 discover. He supposed all the white fibres of the cord conti- 

 nuous with those of brain on the one hand, and with those 



* Recherches Experimentales, sur le Propr. et les Foiict du Syst. Nerveux. 

 2d edit. 1842. 



