M. G. Schlapp 267 
THE SEVEN LAYER TYPE MAY NOW BE COMPARED WITH THE FIVE 
LAYER TYPE (MOTOR AREA) AS FOLLOWS: 
The first layer (layer of glia and tangential fibers, molecular layer) is 
similar in structure to that of the motor area, but is narrower. The second 
layer is similar to that in the motor area. The third is also similar to that 
of the motor region, but is much narrower in many places, especially on 
the convexities of the convolutions. The fourth is a layer of pyknomor- 
phous pyramidal cells, which can be distinguished from the third layer by 
the more intense staining of the cells. This layer does not exist as such in 
the motor region. The fifth layer is Hammaberg’s fourth layer, or the 
layer of granule cells of other authors. Koelliker named it the second 
layer of small pyramids. This layer does not exist in the motor region of 
the brains of the lower animals I have examined; in man just a trace of it 
is seen in the motor region, but it is not sufficiently developed to permit 
one to distinguish it as a separate layer. The sixth layer is again a layer 
of pyknomorphous pyramidal cells, the ganglionic cells of Lewis. This 
layer seems to be a continuation of the fourth layer of the motor region. 
The seventh layer is the inner layer of polymorphous cells. This layer 
corresponds to the fifth of the motor region. 
We therefore have the following layers in the seven layer type: 
1. Layer of gla or outer layer of tangential fibers. 
2. Outer layer of polymorphous cells. 
3. Layer of parapyknomorphous pyramidal celis. 
4. Outer layer of pyknomorphous pyramidal cells. 
5. Layer of granule cells. 
6. Inner iayer of pyknomorphous pyramidal cells. 
Inner layer of polymorphous cells. 
In the dog, the monkey and in man, the transition from the motor to 
the seven-layer type can be distinctly recognized. In man, monkey, and 
dog, less distinctly in the cat, the large pyramidal cells of the motor area 
become smaller at the point of transition and arrange themselves in 
two rows, between which the granule-cell layer (fourth layer of Ham- 
maberg, Ramon y Cajal’s layer of small stellate cells) is distinctly 
seen, giving to this type its characteristic appearance. 
The granule-cell layer is always present in this type. The two layers 
of pyknomorphous pyramidal cells, however, are subject to variation. 
There are places in the cortex where the outer layer of pyknomorphous 
pyramidal cells is wanting and their place is taken by the parapykno- 
morphous pyramidal cells of the third layer, so that in these places the 
fourth layer is absent. Then again, there are places where the inner 
pyknomorphous pyramidal cells are missing and where, more or less 
clearly, can be seen a light stripe, which is known as the inner stripe of 
Baillarger. This condition is most frequently found in the human 
