576 



MANUAL OF HISTOLOGY. 



mm 

 *** 



Fig. 554. Sustentacular 

 connective-tissue from 

 the posterior column of 

 the human spinal cord, 

 showing the nerve- 

 fibres in transverse sec- 

 tion. 



recognised as entering into the composition of this ependymal tissue. 

 They appear to have been formerly incorrectly described as nerve-cells, of 

 which, as well as of nerve-fibres, this tissue is entirely destitute. 



The substantia gelatinosa ofJRolando, mentioned in the preceding section, 

 presents also purely connective-tissue characters. It is remarkable for its 

 richness in cellular elements. Some very few nervous constituents may 

 be observed in it in the form of scattered fibres. 



But the sustentacular substance in the grey matter of the cord is far 

 less pure : it is mixed up with nerve-fibres, ganglion cells, with their 

 various processes, and blood-vessels. It forms here a finely porous spongy 

 tissue, referred to already at 119, of the most delicate texture, with 

 numerous free nuclei or (if the latter still retain a thin layer of protoplasm) 

 with the equivalents of small cells. 



The connective-tissue framework of the white substance, however, 

 attains a greater degree of massiveness. In trans- 

 verse section (fig. 554) it appears homogeneous or 

 streaky, dotted at its nodal points with nuclei, and 

 forming so a lace- work as it were, in whose meshes 

 the transverse sections of the nerve tubes are to be 

 seen ; while in longitudinal cuts a more or less regu- 

 larly tubulated appearance is presented by the slice, 

 which may also show oblong deficiencies of substance. 

 Larger collections of connective substance some- 

 times form radiating partitions around groups of 

 nerve-fibres, giving by their numerous intercommuni- 

 cations a net-like appearance to the whole (fig. 553, h). 

 Towards the periphery of the cord the sustentacular substance is 

 again much more highly organised, and is free from nerve-fibres (Bidder, 

 and Kupffer, Clarice, Koelliker, Frommann). Lastly, the pia mater 



covers the surface of this grey cortical 

 layer. 



Turning now to the Hood-vessels 

 of the cord (fig. 555), it may be 

 usually observed in trans verse sections 

 that from the branches of the art. 

 med. spin, anter. two twigs are given 

 off in the anterior fissure, which 

 pass into the substance of the spinal 

 marrow, and that a third twig, cor- 

 responding to them, lies in the poste- 

 rior fissure (b, c). Other finer arterial 

 tubes are conducted into the white 

 substance (/, g, h) by the radiating 

 bands of connective-tissue of the pia 

 mater. It is from these principally 

 that the capillary interlacements of 

 the white matter are supplied, which 

 are here particularly large meshed, 

 and composed of very delicate tubes. 

 The capillary network of the grey 

 substance is much more dense (d, e). 



6 



J 



Fig. 555. Transverse section in the dorsal region 

 of the medulla spinalis of the cat. a. Cen- 

 tral canal; 6, anterior, c, posterior fissure; 

 rf, anterior cornu; e, posterior cornu; /, y, h, 

 white columns, with their wide-meshed capil- 

 lary networks. 



It is chiefly derived from the arteries of the fissures just named, but is con- 

 nected at all points of its periphery with the vessels of the white substance. 



