266 Microscopie Structure of Cortical Areas 
type in that it can be divided into seven layers, but differs from it with 
regard to the structure of the pyknomorphous or deeply stained pyra- 
midal cells. | 
The motor cortex of the animals studied, presents the following five 
laver type: 
1. Layer of gha or tangential fibers. 
. Outer layer of polymorphous cells. 
Layer of parapyknomorphous pyramidal cells. 
4. Layer of large pyknomorphous pyramidal cells (Betz’s pyramidal 
cells or Lewis’ ganghonic cells). 
5. Inner layer of polymorphous cells. 
The pyramidal cells of the third layer are distinguished not only by 
their smaller size, but also by the structure of their chromatic substance, 
which is more or less reticular. We can therefore designate these cells 
according to Nissl’s nomenclature as arkyochrome cells. The large 
pyramidal cells of the motor area, on the other hand, as well as a great 
number of the pyknomorphous cells of the fourth and sixth layers of 
the parietal and temporal regions present the characteristic sticho- 
chrome structure. 
2 
3 
THE SEVEN-LAYER TYPE. 
It is difficult to give this type a functional name, because it extends, 
in the human brain, over a very large area, in which we must look for 
more than one function. In the human brain it is found in— 
(1) The whole parietal lobe, which we can assume with tolerable cer- 
tainty to be in part the cortical center of sensation. 
(2) The entire lateral portion of the occipital lobe. 
(3) The whole frontal lobe. 
(4) The temporal lobe, wherein a few modifications are found. 
(5) The preecuneus. 
(6) The region of the island of Reil, where again some slight modifi- 
cations occur. 
It is probable that in this cortex are situated the different centers of 
association, which have been described by Flechsig. 
In the brain of the monkey this type.is comparatively less extensive 
in proportion to the well defined motor and visual centers. 
In the cortex of the dog and cat, it occupies a much smaller area and 
is not so clearly defined. Owing to the absence of the frontal lobe in 
these animals, this type is entirely wanting in front of the motor zone. 
In the Pteropus this type is nowhere present in the cortez. 
—— 2 
