XL 
The Lumbar Enlargement of the Spinal Cord. 
Bx JOHN DEAN, M. D. 
(Communicated through Dr. Jerrries Wyman, November 14, 1860.) 
p 
- I proposes, in the following paper, to notice a few points in regard to the structure 
of the spinal cord, confining myself chiefly to a description of the course of the fibres 
forming the nerve-roots, as they pass through the white and gray substances to their 
final union with nerve-cells, discussing somewhat at length the relation which nerve- 
cells and fibres sustain in the cord. 
In drawing up the descriptive details of this memoir I have restricted them chiefly 
to the lumbar region in some of the higher vertebrates, lest any deductions I might 
attempt to establish should be embarrassed by the necessity of comparing observations 
made upon portions of the cord differing somewhat in structure. 
The division commonly made in the substance of the cord into gray and white 
matter, or into vesicular and fibrous, seems to be tenable only when we state the differ- 
ence between them to consist in the presence of true nerve-cells in the gray or vesic- 
ular, while they are absent in the white or fibrous substance. This distinction seems 
to me the only correct one, for I am fully satisfied that the so-called cells of the white 
substance, described by Stilling and others, are nothing more than cells belonging to the 
connective tissue, or, as sometimes occurs, true nerve-cells which have been isolated 
from the gray substance by the plane of section. Bidder* remarks on the situation of 
cells evidently connected with the cornua, that * they are sometimes quite encircled by 
the white substance, in which rare case this substance forms but a very small partition 
separating them from the gray." This every observer will have noticed, and I have 
often in longitudinal sections found such cells quite isolated, which I should have con- 
sidered as belonging to the white substance, had not the section, following a slightly 
* Bidder and Kupffer, Untersuch. über die Textur d. Rückenmarks. Leipzig, 1857. 
VOL. VIII. 43 
