Gland-Cells of Internal Secretion in Spinal Cord of Skates. 9 
Other vacuoles may show fewer large granules, or even a single very 
large one. It thus appears that the amount of this matter is fairly 
uniform in each vacuole. It is apparent also that in the fresh state the 
substance of the granules is soft and under a surface tension that per- 
mits of a union of two or more granules when the precipitate in which 
they lie permits of a close enough contact. This precipitate changes 
from the loose, fine reticulum of the full-sized vacuole to a denser and 
firmer mass which often holds the smaller granules in groups at the 
time the vacuole breaks and discharges its contents. 
It is thus evident that these cells present an appearance greatly 
different from that of any nerve-cells known. A nerve-cell usually pos- 
sesses a large round nucleus, a definite plasmosome, and a relatively 
small amount of chromatin material. Each of these cells, on the other 
hand, possesses an enormous nucleus of the irregular branching type, 
no definite plasmosome, and a large amount of chromatin. In the 
cytoplasm of nerve-cells chromophilic substance in the form of Nissl 
granules can usually be seen; in the cytoplasm of these cells no Nissl 
granules were distinguishable. No neurofibrils could be detected, 
though several special nerve stains were used. Moreover, the general 
staining reactions serve to bring out the fact that there is a definite 
chemical difference in the composition of these cells as compared with 
that of the neighboring nerve-cells. 
Nerve-cells in the spinal cord of fishes are usually located approxi- 
mately opposite or anterior to the structures which they innervate. 
These cells, as has already been pointed out, are present only in the 
caudal portion of the spinal cord from the level of the sixty-fourth 
vertebra to the tip of the tail. If they were nerve-cells, then we should 
expect to find the structures which they innervate in this region of the 
tail. But no special structures of any kind are present here, and here 
only. The electric organs, it is true, are situated in the tail, but they 
extend as far anteriorly as the thirty-third vertebra. The whole ante- 
rior half of the electric organs is anterior to the region of these cells. 
Dissection of the nervous system in the tail of the skate shows that the 
electroplaxes of the electric organs are supplied with nerves which are 
branches of spinal nerves, and these spinal nerves leave the spinal cord 
slightly anterior to the electroplaxes which they innervate. This 
would indicate that the electric motor nerve-cells in the spinal cord 
should be found approximately opposite to the electric organs. It is 
very improbable, then, that these large cells which are located opposite 
the posterior half only of the electric organs could be the electric motor 
nerve-centers. My observations lead me to agree with Ewart that the 
true electric motor nerve-cells are cells which resemble the ordinary 
muscle motor nerve-cells, except that they are larger. 
