No. 1.] SPIVAL NERVES OF THE DOMESTIC PIGEON. 133 
spinal nerves (#;, Fig. 2) as they leave the vertebral column: 
In a series of sections running anteriorly these nerves are at 
first, of course, cut diagonally at some distance from the cord 
itself, since they enter the neural canal obliquely ; and a section 
at that point shows them near to the cord, lying within the neu- 
ral arch (Fig. 9, 2). Passing within the neural canal, the nerve 
does not immediately become attached to the cord, but runs for 
a time quite above it in the dura mater investment ; finally it 
comes to lie within the latter, and passes more anteriorly into 
the pia mater close to the cord, in which it is contained until all 
the fibres have passed into the cord itself, — some distance there- 
fore anterior to the place of exit. So that. while cutting through 
one of the more anterior vertebrze the nerves destined to pass 
out in the next posterior space are found lying beside the cord, 
yet these pass into the structure of the cord before the exit of 
the next anterior pair of nerves from the spinal canal; ze., 
only one pair of nerves lying parallel with the cord will appear 
in any given section. And so the “brush-like” arrangement of 
the nerves from a definite end of the cord, as is found in mam- 
mals, is not strictly the case here, although the point of attach- 
ment of each pair of caudal nerves to the cord is anterior to 
their place of exit from the vertebral column, as in the former 
case. No definite region could be determined as the place 
where the gray matter of the cord begins. It seems rather to 
accumulate insensibly—in sections running forward — about 
the central lumen of the cord until the cornua take their char- 
acteristic shape. Cells belonging to the gray matter are present 
doubtless in greater or less quantities throughout the filum, so 
that the latter seems to be merely a continuation of the cord 
that does not give origin to spinal nerve roots. There seem to 
be no definite tracts in which these ganglion cells are laid, but 
such are definable a little anterior to the elongated origin of the 
roots of the last pair of nerves. The ganglion upon the dorsal 
root of the more posterior pairs of caudal nerves is situated far- 
ther from the neural canal, and is also much smaller, but in the 
more anterior parts of the caudal region the ganglion lies in the 
intervertebral space, and sections pass through it at a very slight 
angle. Such a section taken in s, or s, shows the structure of 
the ganglion lying in the space, as in Fig. 10. Upon the right 
side of the figure the proximal part of the ganglion is cut 
