CHAP. X.] THE SPINAL CORD. 259 



of the brain. When very thin transverse sections are examined 

 with low powers, a good general view of the relative disposition 

 of the gray and white columns is obtained, but we gain no satis- 

 factory information as regards the relation of the elements of these 

 columns (fig. 67). Stilling and Wallaces plates accord generally 

 with the results of our own examinations ; but we cannot admit 

 the accuracy of their interpretation of some of the appearances 

 which they have witnessed and delineated. 



In such a section as that just described, the distinction of gray 

 and white matter is very obvious. From the surface of each horn 

 of the former several lines, of the same colour and general appear- 

 ance as the central mass, pass, in a radiating manner, towards the 

 surface of the cord and to the surface of the fissures (fig. 67). 

 These lines, according to Stilling and Wallach, are continuous with 

 the roots of the nerves, and are nerve-tubes proceeding from the 

 gray matter to form these roots. Their existence, however, in sec- 

 tions made in situations intermediate to the points of emergence of 

 the nerves, shews that this explanation cannot be the true one. 

 Moreover, they radiate over a surface much more extensive than 

 that from which the roots take their rise, and several pass to that 

 part of the surface of the cord which bounds the fissures, and from 

 which it is impossible that they could reach the point of emergence 

 of either root to contribute to its formation. It is not improbable, 

 however, that they may be processes of the gray matter prolonged 

 toward the surface, to which blood-vessels may pass from the pia 

 mater.* 



"We observe in the gray matter numerous nerve-tubes of various 

 size passing among its elements in different directions. Besides 

 these, the branching processes from the caudate vesicles are found 

 here : these processes differ from the nerve-tubes in the absence 

 of the white substance of Schwann, in their grayish colour, in their 

 branching, and in a certain minutely granular texture. Numerous 

 extremely minute fibres, perfectly transparent in texture, may be 

 traced to be continuous with the finer subdivisions of these 

 processes (fig. 56, p. 214). Fibres of the same appearance are 

 occasionally found among the tubes of the white substance of the 

 spinal cord; their connexion with those of the gray matter is 

 unknown. 



Capillary blood-vessels are met with in great numbers ramifying 

 in the gray matter. They are much more numerous in this than 



* Mr. Smee has lately exhibited to us some well-injected preparations, in 

 which thcso lines are shewn to contain vessels. 



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