168 BULLETIN OF THE 
ous in the lateral portions of the cord. Each part also contains nerve 
fibrillee, and the relation of the ganglion cells to each appears to be the 
same. 
There are, moreover, ganglion cells in the ventral nerve cord ; they may 
be conveniently treated of in two groups, which correspond in general 
to those of the brain. The first are simple nervous nuclei, distinguished 
from the nuclei of the surrounding connective tissue especially by the 
intensity with which they take up stains. They are small oval nuclei, 
measuring 4—5 p» by 6-8 p» in diameter, and possessing a prominent nu- 
clear membrane, but not provided with any appreciable amount of sur- 
rounding protoplasm. They are found along the dividing lines between 
the areas of the cord (Plate VIII. Fig. 101) and also on the external 
boundary of the latter, usually closely crowded together ; in cross sec- 
tions they appear as a single or double row; in longitudinal sections 
they are collected into a certain area (Fig. 97). They are about equally 
distributed throughout the length of the cord, and produce the dark 
dotted rows seen on the ventral line in the living animal (Fig.7). 
The large cells of the ventral cord form the second class, and in many 
cases are equal in size to those of the brain. Though not plentiful, 
they are scattered along the whole length of the cord. I was unable to 
find, however, any regularity of distribution, since the interspaces vary 
considerably in extent. Furthermore, they are not plainly paired except 
in rare cases. Usually the successive cells are separated from one another 
by a distance equal to the thickness of ten, or even twenty, cross sections 
(100 to 200). Biirger (p. 641) has described these cells under the 
name of median cells. Ido not think that they begin, as he maintains, in 
the brain; but I agree with him in regarding them as unpaired. These 
big cells are ordinarily found wedged in between the two lateral areas 
and immediately below the ventral portion of the cord (Plate VIII. 
Fig. 101). So far as I have seen, these cells possess each but a single 
process, which passes dorsad between the median and one of the lateral 
areas, but its ultimate fate I was unable to determine. Rarely one finds 
a large cell below the lateral area on one side or the other. In this case 
the nucleus is much flattened dorsoventrally. Biirger regards these 
cells as bipolar. I have seen appearances such as he represents in his 
Figure 13, but do not regard this as decisive, since the two processes are 
not shown, so that, while I have no positive contradictory evidence, [ 
am also unable to confirm his statement. 
The form of the ventral nerve cord may be much altered by collapse 
of the body, which flattens the cord between the two lateral muscular 
