2 24 



NERVOUS SYSTEM. 



[sect. III. 



with a width varying from o*oi'" to o - i"', and of a rounded or 

 triangular form. It lies in the midst of the central grey nucleus, 

 which, with Virchoie, I refer to the ependyma, and consider analo- 

 gous to the thickenings of the ependyma of the brain. This sub- 

 stance is thickest in the lumbar enlargement, and presents a 

 pyriform, scutiform, or heart-shaped figure on a transverse section. 

 The cells embedded in it are, from their stellated form and 

 branched processes, undoubtedly very similar to nerve-cells ; they 

 have, however, frequently as many as five nuclei, and must be 

 ranked with the plasm-cells of the connective tissue. In chromic 

 acid preparations, I have seen cilia upon the cylindrical epithelial 

 cells of the central canal, which observation has been confirmed by 

 Stilling. 



Fig - 95 - The fdum terminate is traversed in its whole 



f~'^\ length by a continuation of the central canal 



of the marrow, and contains, in its upper part 

 true dark bordered nervous fibres. 



G 



™^Lki? 



J 



§ 112. Probable course of the Nerve-fibres 

 in the Spinal Cord. — We have found that the 

 motor and sensitive roots do not terminate in 

 the grey substance of the cord at their point 

 of attachment, as would appear at first sight, 

 but that a part of them turn upwards, and 

 accompany the longitudinal fibres of the white 

 substance. The important question now is to 

 know what becomes of these fibres, whether after 

 a shorter or longer course they terminate in 

 the cord, or whether they all ascend to the 

 brain. As is well known, the majority of in- 

 quirers have been till quite lately of the latter 

 opinion, which was based less upon direct 

 observations, than upon the ground of proba- 

 bility, until Volhnann, in his justly celebrated 

 article, ' Nervenphysioloyie / Wagner's Hand- 

 worterb. d. Physiol., vol. ii., shook it to its 

 foundation, carrying the majority of physiolo- 

 gists with him. I have, however, shown, that 

 Volhnann 's arguments are not sufficient ; and from this time a 

 series of new investigations have been made, from which it 

 appears to become more and more evident, that a part of the 

 fibres of the spinal nerves come from the brain, whilst another 

 arises or ends in the cord itself. 



€ 



Five transverse sec- 

 tions through a human 

 spinal cord, hardened 

 by chromic acid, to 

 show the relative pro- 

 portions of the gray 

 and white substances, 

 of natural size. A. 

 From the conns me- 

 dullaris. B. From the 

 lumbar enlargement. 

 C From the dorsal 

 part. D. From the 

 cervical enlargement. 

 E. From the superior 

 cervical portion. 



