330 THE SPINAL CORD, BY J. GEBLACH. 



Of great importance for the understanding of the spinal 

 cord is the proportion in point of bulk of the white to the 

 grey substance. This is by no means identical in different 

 parts of the organ. From a comparative examination of 

 transverse sections made at different heights it may be clearly 

 seen that the enlargements presented by the cord in the 

 cervical and lumbar regions are chiefly attributable to an 

 increase in the quantity of the grey substance. The com- 

 parison of such sections further teaches that the quantity of 

 white substance gradually but almost imperceptibly increases, 

 from below upwards, as is convincingly shown by a comparison 

 of the grey and white substances in the three adjoining 

 photographically correct sections of the human cord in the 

 cervical, dorsal, and lumbar regions (fig 218). 



In the progressively diminishing conus medullaris the white 

 substance steadily decreases in relation to the grey matter, 

 until where the point of the spinal cord is continuous with 

 the filum terminale the white substance almost entirely 

 vanishes. 



The white substance of the spinal cord is composed of nerve 

 fibres, of large and medium size, and of connective tissue and 

 bloodvessels, whilst the grey substance contains, in addition, 

 a large proportion of the finest nerve fibres with which I am 

 acquainted, and which are united in a plexiform manner with 

 nerve cells.* Of the elements that are not of a nervous nature, 

 besides the vessels, which are found to be much more numerous 

 in the grey than in the white substance, the capillaries 

 forming a much closer plexus, there are present epithelial cells 

 lining the central canal, and connective tissue, which exists in 

 considerable quantity both in the immediate neighbourhood 

 of the central canal (fig. 217, 6) and in the posterior cornua, 

 as the substantia gelatinosa of Rolando (fig. 217, s). 



* In the dorsal region of the human spinal cord, small isolated nerve 

 cells occur in the connective-tissue septula of that portion of the lateral 

 column which is in close proximity to the grey substance. Such cells are 

 very abundant in the spinal cord of the Ox and Sheep. 



