272 



FUNCTIONS OF THE NERVOUS SYSTEM. 



sures, but by two furrows on each side, marking out three columns upon it. 

 We have, therefore, on each half of the cord, an anterior middle or lateral 

 and posterior column. The points of the crescentic lamellae of grey matter 

 approach these furrows pretty closely ; but elsewhere the grey matter is 

 covered deeply by the fibrous columns. Each spinal nerve arises from two 

 sets of roots. The anterior roots join the spinal cord, near the anterior fur- 

 row ; and the posterior, near the posterior furrow. Respecting their intimate 

 connection with the principal divisions of the cord, a considerable diversity 

 has existed among the statements of anatomists ; but it seems to be now 

 generally admitted, that, as in the Articulata, a part of each root enters the 



[Fig. 134. 



Fist. 135. 



Transverse section of human spinal cord, close to 

 the third and fourth cervical nerves ; magnified ten 

 diameters, (from Stilling;)-/. Posterior columns, ii. 

 Gelatinous substance of the posterior horn. k. Pos- 

 terior root. I. Supposed anterior roots, a. Anterior 

 fissure, c. Posterior fissure, b. Grey commissure, in 

 which a canal is contained, which, according to these 

 writers, extends through the length of the cord. g. 

 Anterior horn of grey matter containing caudate vesi- 

 cles, e. Anlero-lateral column (from k to a)]. 



Passage of Nerve-fibres through the 

 Spinal Cord, according to Stilling; A, 

 posterior fibres continuous with the 

 anterior of the same side, through the 

 nucleus of the cord ; B, posterior fibres 

 continuous with the anterior of the 

 opposite side. 



grey matter or ganglionic portion of the cord, whilst a part is continuous 

 with its white or fibrous columns. The course of the fibres which enter the 

 grey matter, has been lately displayed, in part, at least, by the researches of 

 Dr. Stilling.* It appears that of the fibres of the posterior roots, some form 

 loops in the grey matter, and become continuous with those of the anterior 

 roots of the same side, as seen at A, fig. 135. Others cross the grey matter, 

 and become continuous with those of the anterior roots of the opposite side, 

 as seen at B. It can scarcely be doubted that these fibres, being unconnected, 

 with the brain, constitute the system to which reflex actions are due. Although 

 Dr. Stilling's inquiries have not proved the fact,t yet it may be inferred from 

 physiological phenomena, as well as from the facts recently shown by Mr. 

 Newport ( 326), that there are other fibres, which pass from' the posterior 



* Ueber die Textur und Function der Medulla Oblonirnta. 



f It may be thought that the mode of examination which he adopted, that of making 

 very thin transverse sections of the Spinal Cord, is not well fitted to display the connections 

 of the roots with longitudinal fibres. The subsequent observations of Budge (Muller's Ar- 

 chiv., 1844, p. 160), seem to have established the fact of the continuity of a portion of each 

 root with the longitudinal fibres of the cord. 





