Gland-Cells of Internal Secretion in Spinal Cord of Skates. 27 
bodies” of the spinal cord in the region of these large cells are to be 
explained in this way. 
Another striking peculiarity is the occasional occurrence of a portion 
of the cell inside the central canal. Figure 42 is a photograph of such a 
ease. In this section the central canal is almost entirely filled with a 
part of one of these large gland-cells, both cytoplasmic and nuclear 
material being present, as well as some of the granular material. It 
was suggested to the writer by C. J. Herrick that these cells might have 
something to do with Reissner’s fiber, perhaps representing the mechan- 
ism for renewing or regenerating Reissner’s fiber in the posterior part of 
the cord. No real evidence has been found to support this hypothesis, 
however. None of the large cells are present in the anterior portion 
of the spinal cord or in the mid-brain, which is the anterior limit of 
Reissner’s fiber. It would be expected that some of the cells would be 
present in these regions if this hypothesis were true. Furthermore, 
the granular secretion of the cells is rarely found in the central canal, 
so that it is improbable that it has any connection whatever with 
Reissner’s fiber. 
Another morphological peculiarity of the cells is the occasional pres- 
ence in the nucleus of several plasmosome-like bodies. Several of 
these are indicated in the cell of figure 48. That these are not true 
plasmosomes is shown by their staining reactions. Their exact signifi- 
cance is unknown. E. G. Conklin has suggested that they may repre- 
sent excretory products, formed perhaps as a result of unusual activity 
of the nucleus. 
In the cytoplasm of this same cell are a few ependymal fibers. It 
has been observed in several other cases that ependymal fibers have in 
some way become incorporated in these large, irregular cells. As the 
cells are bounded by no definite cell-membrane they are rather loosely 
integrated, and assuming that they are capable of a limited amount 
of movement, it is easily conceivable how they might come to include 
some of the neighboring ependymal fibers. 
EFFECT OF AMPUTATION OF THE TAIL. 
The following experiments were made in order to discover whether 
these gland-cells with their secretion were of vital importance to the 
skate: The tails of 12 skates were cut off just anterior to the region 
containing the cells. The caudal artery was plugged with cotton to 
prevent excessive loss of blood, and the animals then placed in a large 
aquarium.! At the end of 48 hours the skates began to die. At the end 
of a week only 2 were still alive. The last one died at the end of 19 
days. Most of the animals undoubtedly died as the result of injury 
caused by the operation. The fact that one of them lived for 19 days 
SG STS PRE ToL VOOR ny NE OE SS A 
1This large aquarium was the “dogfish pool’’ at the United States Bureau of Fisheries 
Station, Woods Hole, Mass. 
