THE MICROSCOPIC STRUCTURE OF CORTICAL AREAS IN 
MAN AND SOME MAMMALS. 
BY 
M. G. SCHLAPP, M. D. 
Instructor in Histology and Pathology of the Nervous System, 
Cornell University Medical School. 
WitTH 4 PLATES. 
INTRODUCTORY. 
The first step toward dividing the cerebral cortex into structural 
areas corresponding with the functional localization, determined by the 
experiments of Fritsch and Hitzig, was made when the giant cells of 
Betz were discovered and found to be characteristic of the motor area. 
These cells, described by various authors for man, were later identified 
by Bevan Lewis in the pig, sheep, cat and other animals, and found to 
be also present in isolated groups behind the motor area. 
Nissl’s method of staining nerve cells has, as I believe, furnished us 
with a means of carrying such investigation further than was possible 
py the older technique. 
We are as yet unable to distinguish specific differences between cor- 
tical nerve cells. It is, for instance, impossible to show such a differ- 
ence between cortical nerve cells in the auditory and those in the visual 
path. We can, however, say that the entire cortical visual center, con- 
sidered as an organ, differs from the auditory or other cortical centers. 
In order for us to determine whether any relation can be shown be- 
tween the variations in the structure of the different regions in the 
cortex, on the one hand, and the function of these respective regions on 
the other hand, we must examine the largest possible number of brains, 
not only of those of one species of animals, but also those of animals in 
different stages of phylogenetic development. 
From such comparative studies it has been found to be true that in 
animals whose organs of sense are equally well developed, but have not, 
on the whole, reached a high degree of specialization, no great differ- 
ences in the structure of the cortex can be observd. This seems to be 
the case with the brain of the pteropus, the cat, and somewhat less so 
of the dog. On the other hand, in correlation with the special develop- 
