Gland-Cells of Internal Secretion in Spinal Cord of Skates. 31 
that have been discharged by vacuoles and are now in the tissues of the cord. The end of a large 
gland-cell may be seen at each side of the figure. A much larger amount of granular material is 
normally present in Raia levis than in Raia ocellata. Photograph 438. 
Fic. 23.—Cross-section of spinal cord of Raia ocellata, after stimulation with electricity for 10 
minutes. Much more than the normal amount of granular material is present. The cell which 
produced this is not shown in this section. It was present, however, a few sections farther on. 
Photograph 530. 
PLATE 7. 
Fic. 24.—Cross-section of spinal cord of Raia ocellata, after stimulation with electricity for 5 
minutes. The animal was killed 10 minutes later. One of the large gland-cells has crowded aside 
the central cells. Reissner’s fiber, which is ordinarily inside the central canal, is here shown 
entirely inclosed by the cytoplasm of the cell. Granular secretion is also present in the tissues of 
the cord. Note also the peripheral distribution of the nuclear material of the cell. 490. 
Fig. 25.—Cross-section of spinal cord of Raia ocellata after stimulation with electricity for 2 
minutes. A large gland-cell is present just dorsal to the central canal. A large, irregular vacuole 
is to be seen filled with precipitate, some of which is light-staining and some dark-staining. Down 
near the ventral edge of the cord are to be seen 2 vacuoles filled with dark-staining precipitate. 
These have also probably been produced by the cell. Another vacuole filled with mature gran- 
ules is also present in the cyptoplasm of the cell. 612. 
PLATE 8. 
Fics. 26—41.—A series of vacuoles taken chiefly from skates stimulated with electricity or 
pilocarpine, illustrating the complete history of the vacuoles and granules. 
Figs. 26-32.—These show the growth of the vacuoles which at first are filled with a clear fluid, 
later with precipitate which stains much like the cell cytoplasm. This precipitate later becomes 
thread-like and granular, staining at first lightly, then taking a deep iron-hematoxylin stain 
(figs. 33-35). 
Fics. 36-38.—These are taken from Raia levis. Figure 36 is here inserted to show the definite 
membrane that surrounds the vacuole. The cell cytoplasm has shrunk away from the vacuole, 
bringing the membrane plainly into view. Figure 37 represents a fully ripe vacuole containing 
granules about to be discharged. Figure 38 shows a single large granule and a few smaller 
ones. The large one has been formed by fusion of many smaller ones and, as can be seen from 
its staining reactions, the fusion is not entirely complete. 
Fics. 39—41.—Vacuoles outside the cell. Figure 39 shows one that must have been isolated 
from the cell which produced it while it still contained the light-staining precipitate, before any 
ripe granules had formed. Figure 40 shows a vacuole that was isolated from the mother cell just 
as the light-staining precipitate was being replaced by very small dark-staining granular material. 
Figure 41 shows a vacuole containing ripe granules partially fused together. Although the vacuole 
is ripe the vacuolar membrane has not yet broken. 1012. 
PLATE 9. 
Fig. 42.—Cross-section of spinal cord of Raia ocellata, after stimulation with electricity for 2 
minutes. A part of one of the large gland-cells has in some way entered the central canal and fills 
it up almost entirely in this section. Note also how the cell-body and even the chromatin gran- 
ules of the nucleus have been drawn out ventrally, as if the cell had recently moved in this direc- 
tion. Photograph 530. 
Fie. 43.—Cross-section of spinal cord of Raia oecllata, after stimulation with electricity for 2 
minutes. In the nucleus may be seen several of the unknown plasmosome-like bodies. Note also 
the ependymal fibers apparently running through the cell cytoplasm. Photograph 530. 
