260 Microscopie Structure of Cortical Areas 
ment of a given sense organ, the corresponding cortical area presents a 
marked specialization as compared with the surrounding regions. In 
the brain of the horse, for instance, the olfactory region seems to be very 
highly developed, and is plainly distinguishable from the remaining cor- 
tex. The other organs of sense in that animal do not seem to have 
reached such a high degree of development, and the cortical areas corre- 
sponding to these organs are accordingly less developed and less marked. 
In the brain of the monkey and of man, we find several regions charac- 
teristically developed and sharply defined, a fact which corresponds to 
the development of the sense organs associated with these several regions. 
Much confusion has arisen in comparing the findings of different 
investigators who have used dissimilar methods. 
Another source of error hes, I believe, in the fact that only small 
pieces of the cortex taken from different regions were examined. There 
have never been made, to my knowledge, entire sections through the cere- 
bral cortex, especially that of the human brain, for this purpose, and on 
that account a continued picture was not obtained. The sections which 
I have prepared were made through the entire hemisphere, frontally, 
horizontally, as well as sagittally, thus presenting a nearly continuous 
picture. A disadvantage of these entire sections, however, is met in the 
fact that in many places the cortex was not cut perpendicularly, and 
hence the cells assumed a different shape. These pictures can be easily 
recognized, however, if one has a little experience in microscopy of the 
cerebral cortex. The principal cause of the general lack of agreement as 
to the structure of the cortex is, however, due to the laying down of 
general conclusions drawn from a study of the brains of lower animals 
without sufficient comparison with the human cortex which is very 
specially constituted. 
The investigations of Fritsch and Vitzig in 1870 followed by those 
of Munk, Ferrier, Hitzig, Goltz, Flechsig, Duret, Carville, Luciani, 
Tamburini, Horsley, Schafer and others have furnished us with a solid 
experimental basis for a localization of function in the cerebral cortex 
of the lower animal; while the results of human clinico-pathological 
cases, which have lately been examined as extensively as our methods 
will permit, have made it possible to institute valuable comparisons 
here. If, however, we undertake to compare the results of our experi- 
mental investigation of animal brains with those obtained in clinico- 
pathological cases of human brains, we must not forget that the differ- 
ent centers vary in animals and man and also among animals them- 
selves, with regard to their situation in the cortex. Such variation is 
to be explained by the fact that a specially developed cortical center in 
