54 
BULLETIN OF THE LABORATORIES 
columns to be quite different in having much larger fibres with a con- 
siderable amount of surrounding neuroglia. 
The ventral root-zone is represented in Plate XIII, Fig. 2, and is 
found to spread out over the greater part of the lateral aspect of the 
cord. The ventral root does not leave the cord as a distinct bundle, 
as is the case with the dorsal root, but is formed from an extension of 
the fibres from the whole side of the ventral cornu, which radiate to 
the surface of the cord and then converge to the ventral root. 
The dorsal root enters as a large bundle. Part of its fibres pass 
into the dorsal root-zone or Burdach’s columns and part pass directly 
into the dorsal cornu and there enter the cells. of the gray matter, while 
part pass directly to the opposite side through the posterior commis- 
sure. 
The distribution of the gray matter is essentially the same as that 
of the rabbit. The ventral cornu is rather broad but very short and 
contains two groups of multipolar cells. One median group (Plate 
XIII, Fio. I, <2, Fig. 3, Fig. 4, and Fig. 8,) is situated at the median 
angle of the cornu, having cells from .015 to .02 mm. in transverse 
diameter. These cells send off processes to the ventral columns, which 
eventually pass into the ventral roots, also processes which seem to 
pass to the dorsal cornu, and some which pass through the ventral com- 
missure to the opposite side. 
The other cell group (Plate XIII, Fig. 4 c. Fig. 9,) is situated 
external to the first and forms a lateral nucleus Tne cells resemble 
those of the median group very closely and send their processes in the 
same directions. 
The cells of the gray matter of the dorsal cornu are much smaller 
than those of the ventral. They occur in greatest numbers in the cer- 
vix of the cornu (Plate XIII, Fig. i, /^, Fig. 2, Fig. 4, ^/, Fig. 5.) 
These cells are from .005 to .01 mm. in transverse diameter and are 
multipolar in form. The processes to which they give origin follow 
the direction of the fibres in which the cells are imbedded, but whether 
they are simply the nodal points of these fibrqs and do not represent 
true cells may be questioned. They are nucleated and, except in size, 
resemble very closely the motor cells of the anterior cornu. Besides 
these distinct cell groups there are also numerous cells scattered 
rather irregularly throughout the gray mass, and at the exits of 
the ventral roots. These cells, which lie lateral to the central canal, 
increase greatly in number and size and appear to form a large nucleus 
