MEDULLA OBLONGATA. 569 



different functions ; the anterior witii that of motion, the poste- 

 rior that of sensation, and that the same division exists in regard 

 to each half of the spinal column, though it has not been proved 

 upon what part of the side of the medulla the line of demarca- 

 tion exists. The deep lateral fissure, where the posterior roots 

 of the nerves emerge, has been assumed as dividing each half of 

 the spinal marrow into a posterior column, and an antero-lateral ; 

 the posterior made up as experiments upon living animals would 

 seem to show, wholly of fibres of sensation, and the latter com- 

 posed on its front part exclusively of fibres of motion ; the fibres on 

 the back part of the latter or antero-lateral column adjoining the 

 posterior roots of the nerves, belonging to the column of sensation. 

 We are therefore justified in considering with Solly and other 

 recent writers, that the line of division between the fibres of sen- 

 sation and those of motion, though unmarked, exist somewliere 

 in the middle between the two orders of roots of the nerves. 

 The absence of any tnarked line of division between the motorial 

 and sensorial columns, being no evidence against this view, as 

 nervous fibrils, when in juxtaposition have no intercommunication. 

 — ^The two lateral fissures cannot well be traced up on the sides 

 of the medulla oblongata, in consequence of their being oblite- 

 rated by some curved transverse fibres,* concave on their up- 

 per part, which seem to come from the corpora pyramidalia, 

 and run over to the cerebellum. But a division of the medulla 

 upon the side exactly between the roots of the nerves, extended 

 upwards by tearing, in parts that have been prepared for dis- 

 section, has a tendency to separate between the corpus olivare 

 and the corpus innominatum. From this it may be considered 

 probable, that all in front of this division, forms the motorial 

 column, and all behind it the sensorial. For facility of de- 

 scription, however, it is best to take the posterior median fis- 

 sure as the line of division, and treat of the posterior column 

 and the antero-lateral column. 



* These fibres have been called arciform or bow-shaped, by Santorini and 

 Rolando ; and by Solly, the cerebeller fibres of the anterior columns. But the 

 observations of Cruvielhier, render it probable, that these fibres come from the 

 vertical septum of the medulla, described and figured by Sir C. Bell, in the 

 T «r>M„n Philos. Trans, for 1834. 



48* 



