64 
MAMMALIAN ANATOMY 
power. Beginning with the most external layer, the layers of the 
retina are named and constituted as follows: 
i. The pigment layer (outside of this, the chorioid coat, 
also pigmented, and the sclerotic, are present in some 
of the preparations). 
ii. The layer of rods and cones, their apices directed toward 
the pigment layer. 
iii. The external limiting membrane, a delicate line, scarcely 
visible, and consisting mainly of the branches of the 
neuroglia, i.e., supporting cells. 
iv. The outer nuclear layer, a conspicuous layer exhibiting 
many deeply stained nuclei which are, for the most 
part, those of the nerve cells of which the rods and 
cones are the highly specialized processes. Among 
these, and indistinguishable in these preparations 
from them, are nuclei of neuroglia cells. 
v. The outer molecular layer, finely granular in appearance, 
because it consists of the cut ends of the delicate 
branches of the cells of the nuclear layers between 
which it lies. 
vi. The inner nuclear layer, consisting of bipolar nerve cells, 
the deeply stained nuclei of which give the name to the 
layer. 
vii. The inner molecular layer, with a structure similar to 
that of the outer molecular layer. 
viii. The ganglion cell layer, consisting of ganglion cells the 
rather large nuclei of which indicate the extent of the 
layer. 
ix. The nerve fiber layer, consisting of the fibers of the 
optic nerve, which are for the most part neurites of 
the cells of the ganglion cell layer. These fibers con¬ 
verge from various parts of the retina toward the point 
of exit of the optic nerve on its way to the brain (i.e., 
the blind spot). 
Compare these slides with the pictures in the various text¬ 
books of histology, and with the laboratory charts. Draw a 
