272 Microscopie Structure of Cortical Areas 
cortex an enormous number of granule cells appear. The second, third 
and fourth layers can at first sight be distinguished only indistinctly ; 
but after a more careful examination of the field one does see that in 
the second layer the cells are set more closely together than in the third, 
and, owing to that again, the fourth layer becomes more conspicuous. 
Besides, there are in this fourth layer somewhat larger cells than in the 
second and third. Below the fourth layer one sees very plainly a layer 
of tangential fibers (the stripe of Baillarger), in which here and there 
are found large, fusiform, irregular cells. Then, below this layer, there 
is a very conspicuous and marked granule-cell layer. Then follows 
another layer of tangential fibers (inner stripe of Baillarger), in which 
again here and there are found large fusiform cells. Lastly, the inner 
layer, or layer of polymorphous cells, differs from the layer of polymor- 
phous cells in the parietal and motor regions. It is almost twice as 
wide as in the above mentioned two types; is more sharply marked by 
the great number of cells found therein, and besides there are seen seat- 
tered here and there large, intensely stained, irregular cells which have 
been described by Meynert, who named them “ solitary cells.” 
There are, therefore, six layers, if we consider the second, third and 
fourth layers as one. If we, however, count each one separately, then 
there are eight layers, as follows: 
1. Layer of glia cells, or outer layer of tangential fibers. 
2. Outer layer of polymorphous cells. 
3. Layer of parapyknomorphous pyramidal cells (here, however, the 
cells have a more irregular shape). 
4, Layer of granule cells, with somewhat large, irregular cells, among 
which are also found pyramidal cells. 
o. Layer of tangential fibers (outer stripe of Baillarger), in which 
stripe irregular cells are found. 
6. Layer of granule cells (inner layer). 
7. Layer of tangential fibers (inner stripe of Baillarger). 
8. Layer of polymorphous cells (inner layer). 
In the dog and the eat the visual cortex is not plainly distinguishable 
from the remainder of the cortex. One can see, however, that it con- 
tains more granule cells than the parietal cortex. Another fact which 
strikingly coincides with this is the corresponding lack of development 
of the lateral geniculate body in the brain of the dog and cat 
In the monkey, whose visual cortex is very highly developed, the de- 
velopment of the lateral geniculate body is correspondingly more 
marked than in the dog and cat. The lateral geniculate body of the 
human brain is like the monkey’s. 
