18 Papers from the Department of Marine Biology. 
movement of a part of the cell-mass in a ventral direction has recently 
taken place. The chromatin granules are drawn out in threads in the 
direction of the medial ventral process and the whole aspect of the 
nucleus suggests that the cell has moved ventrally. 
It should be kept in mind that the cells of the skate are found from 
embryonic stages on up through adult life. The tubercle cells, on the 
other hand, are of very recent origin, 2. e., they originate shortly after 
the tubercle bacilli become present. This may be one way of account- 
ing for the difference in the appearance of the nuclei of the two kinds 
of cells. With longer duration the nuclei of the tubercle cells might 
fuse and come to resemble more and more the single branching nucleus 
of the skate cells. 
The morphological similarities, therefore, of the giant tubercle cells 
and of the large cells of the spinal cord of the skate are close enough to 
justify experimental work that might throw some light upon the ques- 
tion of whether or not the two are also physiologically similar. 
Skate 60. A 1 per cent aqueous solution of trypan blue was injected intraperitoneally; 
19 hours later a second injection was given, and 24 hours later a third was given. The skate 
died overnight and the spinal cord was fixed in 10 per cent formol. Sections showed that 
no trypan blue had been taken up by these large cells. 
Skates 67, 68. These animals were given the same treatment described above. The cells 
showed no trace of the dye. 
Skate 36. One injection was given and the animal killed at the end of 42 hours. At this 
time there could be no doubt as to the success of the injection, as the whole skate was 
colored blue, including the tail. No trypan blue was found to be taken up by the cells in 
question. 
Skate 38. One injection was given and the animal killed at the end of 5 hours. The cells 
showed no trace of the dye. 
Skate 74. The spinal cord was exposed in the region of these cells near the first little tail-fin. 
Trypan blue was injected into the vertebral canal and into the small spinal vein on the 
dorsal side of the cord. At the end of 30 minutes the spinal cord was fixed in 10 per cent 
formol. The dye had not entered any of the large cells. 
Skate 138. Trypan blue was injected into the spinal vein which lies on the dorsal side of 
the spinal cord. The injection was made in front of the first little tail-fin. The skate was 
kept alive for 10 hours and then pieces of the spinal cord fixed and examined. The dye had 
not been taken up by any of the large cells. 
Skate 189. The animal was treated in the same way as skate 138. Pieces of the spinal 
cord were taken at the end of 10 hours. The skate was then kept alive for 22 hours more 
and other pieces of spinal cord then fixed. In neither case did the large cells show any trace 
of the dye. 
These experiments indicate that the large cells of the skate do not 
belong to the macrophage group of Evans. In no case in the eight 
animals used was the dye taken up by these cells. It is well known 
that the blood-stream of the central nervous system is rather isolated 
from the rest of the circulation, and the objection may be raised that 
the vital dye did not get into the blood-stream of the spinal cord. Some 
of the neural blood-vessels, however, showed traces of the dye, and in 
one case in particular endothelium of capillaries well toward the central 
portion of the spinal cord took the vital stain, showing that in this 
animal at least the dye had permeated the vessels of the cord. 
