THE SPINAL CORD 



33 



Plate XIII. shows a number of cells of the neuroglia in the cord. The neuroglia is 

 admitted by all authorities to be a sort of supporting framework extending through the entire 

 nervous system, giving support to the neurons. It was formerly supposed that the neuroglia 

 was a sort of connective tissue, but the researches of Golgi and His * have shown that it 

 originates in the embryo from the ectoderm, the same layer which develops into the nervous 

 system. The neuroglia develops from the ependymal cells lining the central canal, which send 

 out long fibre-like offshoots extending to the periphery of the cord, and forming a sort of scaf- 

 fold (Fig. 5). These are shown 

 on the left side of the figure. 

 They do not enter the posterior 

 horns or columns. In addition 

 to this scaffold there develop in 

 the cord spider-like cells with long 

 projections, and these are shown 

 in Plate XIII. The enormous 

 number of these cells, and their 

 grouping in the fcetal cord is 

 shown in Figure 5, taken from 

 Lenhossek. He has shown 2 that 

 these cells develop from the epi- 

 thelial layer of the embryo, like 

 the nerve cells themselves. A 

 large number of these glia cells 

 cluster about the central canal of 



the cord, forming a dense interlac- 



FIG. 5. 



FlG. 5. (Lenhossek.) Neuroglia cells and fibres of the spinal cord of a human embryo 



14 cm. long. 



On the left half the long, straight fibres developing from the epithelial cells lining 

 the central canal are shown. On the right half the large number of neuroglia cells devel- 

 network of 2"Ha fibres known P' n 8 within the cord and sending their fibres through it are seen. 



as the gelatinous substance of Rolando. No special function can be assigned to this region. 

 These glia cells appear to play a considerable part in the pathological processes which go on 

 in the cord. Their abnormal increase gives rise to gliosis in the gray matter, and to sclerosis 

 in the white matter. 



1 His, Arch, fur Anat. u. Phys., Anat. Abth., 1890, s. 103. 



2 M. v. Lenhossdk, Verhandl. d. Anat. Gesellsch., 5 Versammlung, 1891, Anat. Anzeiger, 1891, s. 193. 



