708 NERVOUS SYSTEM. (MICROSCOPICAL ANATOMY OF THE NERVOUS CENTRES.) 



the direction of which is probably oblique or 

 transverse, as considerable portions of them 

 may be seen taking such a direction when a 

 piece of grey matter, cut transversely, is exa- 

 mined under the microscope. 



The grey matter of the cord contains caudate 

 and spherical vesicles imbedded in their usual 

 granular matrix. They are found in the horns 

 as well as in the commissure. The caudate 

 vesicles are most numerous, and distend in the 

 anterior horn and at the root of the posterior 

 one. The remainder of the posterior horn and 

 the gelatinous substance which is found at its 

 posterior border, resemble very closely in struc- 

 ture the grey matter of the cerebral convolu- 

 tions. 



By examining thin transverse sections of the 

 cord, carefully hardened by immersion in 

 spirits, a good view of the relative disposition 

 of the grey and fibrous substances may be ob- 

 tained. Stilling has carried investigations of 

 this kind to a great extent, and has published 

 some beautiful plates, which are quite true to 

 nature. Fig. 396 is copied from one of them. 



Fig. 396. 



Transverse section of human spinal cord, close to the 

 third and fourth cervical nerves. Magnified ten dia- 

 meters. (From Stilling.) 



f, posterior columns; i i, gelatinous substance of 

 the posterior horn ; k, posterior root ; /, supposed 

 anterior roots ; a, anterior fissure ; c, posterior 

 fissure; b, grey commissure, in which a canal is 

 contained, which, according to these writers, ex- 

 tends through the length of the cord ; y, anterior 

 horn of grey matter containing vesicles ; e, an- 

 tero-lateral column, from k to a. 



It is impossible, however, to obtain any 

 information from such examinations, except 

 of the most general kind. On referring to the 

 figure, the reader will perceive several lines, of 

 the same colour and appearance as the central 

 mass, to radiate from each horn of the grey 

 matter to the surface of the cord, and not only 

 to its external surface, but to that of its fissures. 

 At whatever part of the cord the section be 

 made, whether on a level with the roots of the 

 nerves or between their points of emergence, 

 the same appearance of radiating lines is seen, 

 and the radiation will be found to extend be- 

 tween the central grey matter and whatever 



part of the surface of the cord the pi a mater 

 comes into contact with. 



Stilling and Wallach suppose that these lines 

 are continuous with the roots of the nerves; 

 that they are, in fact, nerve -tubes proceeding 

 from the grey matter to form these roots. But 

 this supposition seems quite untenable, for the 

 following reasons : 1st, because these lines are 

 met with in situations intermediate to the points 

 of emergence of the nerves ; 2dly, because they 

 pass to situations, such as the surface of the 

 fissures, from which no nerve-roots emanate; 

 3d!y, because, if they were nerve-tubes, they 

 could not be so distinctly seen with so low a 

 power. It is much more probable that they 

 may be processes of grey matter prolonged to- 

 wards the surface, to which bloodvessels may 

 pass from the pia mater, or simply bloodvessels 

 passing from the pia mater to the grey matter. In 

 some well-injected specimens, which Mr. Smee 

 had the goodness to shew me lately, the blood- 

 vessels were seen to take exactly the same 

 direction and course as these lines. 



Besides the nerve-tubes which are found in 

 considerable numbers in the grey matter, the 

 branching processes of the caudate vesicles are 

 met with in it also, which may be distinguished 

 from the nerve-tubes by the absence of the 

 white substance of Schwann, by their greyish 

 colour, by their branching, and by their minutely 

 granular texture. Capillary bloodvessels are 

 met with in great numbers, ramifying in the 

 grey matter, where they are much more nume- 

 rous than in the fibrous matter. 



Stilling and Wallach describe a canal passing 

 through the centre of the grey commissure, and 

 extending the whole length of the cord. This 

 is certainly visible in most regions, but not in 

 all. It seems to me to have much more the 

 appearance of a bloodvessel than of a canal. 

 According to these authors, it is the persistent 

 condition of the much-talked of canal of the 

 spinal cord referred to at a previous page. Its 

 situation in the grey matter seems rather op- 

 posed to this view. The point, however, is 

 one upon which I am not prepared to express 

 a decided opinion at present, and which de- 

 serves more extended careful examination. 



From a review of the preceding statements, 

 it is plain that a large number of fibres pass 

 into the grey matter of the cord, and probably 

 form some intimate connection with its minute 

 elements; and this fact is favourable to the 

 supposition that the spinal nerves derive their 

 origin, at least partly, from the grey matter. It 

 must be admitted, either that these fibres unite 

 with the vesicles of the grey matter in some 

 way, or that they pass up to the brain through 

 the grey matter; the former seems the more 

 reasonable supposition, and more consistent 

 with the apparent oblique or transverse direc- 

 tion which the fibres take in the grey matter. 



The minute structure of the medulla oblon- 

 gata resembles in many particulars that of the 

 spinal cord. There is not, however, so com- 

 plete an isolation of the fibrous matter in it as 

 in the latter. Excepting in the anterior pyra- 

 mids, and quite on the posterior and lateral 

 surfaces, the two kinds of nervous substance 



