494 . Dr. F. W. Mott and Miss A. M. Kelley. [ Mar. 6, 
noticeable that just as in the occipital region there is no definite Affenspalte 
present forming a boundary to the visual area, so in the central region there 
is no fully formed fissure making a sharp line of demarcation between the 
motor and post-central areas. 
LTV. HISTOLOGICAL DESCRIPTION OF THE CORTEX. 
Summary of Histological Description of the Cortex. 
By comparing the camera lucida drawings of typical strips of cortex of 
the frontal, motor, post-central, visual, temporal, and hippocampal areas (vide 
Plates 14—18),* it will be seen that although the differences in the types are 
not so pronounced as in the higher apes and man, it is evident that each of 
these areas has a characteristic lamination. The cortex of the archipallium 
being peculiar both in its lamination and in its cell elements, is easily mapped 
out. The motor area is characterised by the Betz cells; the frontal area by 
a comparative poverty of cells, both in size and number; and neither the 
frontal nor the upper part of the motor area possesses a definite layer of 
granules. The sensory areas, on the other hand, are distinguished by a rich 
granule layer; and of these the wiswal area is marked by the large solitary 
cells of Meynert and the line of Gennari; the post-central area by a line of 
large pyramids below the granules; and the temporal area shows a line of 
peculiar elongated pyramids which are especially large and conspicuous in 
the region about the posterior end of the Sylvian fissure. A detailed 
description of the histology of these areas is given below. 
These typical forms of lamination are found in regions which have been 
termed “focal.” They are generally surrounded by a cortex less typical or 
“peri-focal.” Between some types (for example, the motor and post-central) 
the peri-focal area of the one merges into the peri-focal area of the other, 
with the result that there is a region between the two which shows mixed 
characteristics. We have found that, in the lemur’s cortex, there are few 
definite border lines where one type of cortex ends abruptly and another 
begins. On microscopical examination of the Rolandic region of the ape’s 
cortex the change from the motor to the post-central type can be readily 
observed (the base of the fissure of Rolando forming the approximate 
boundary). In the lemur the motor cortex merges very gradually into the 
post-central type. This is the case with most of the areas within the 
neopallium. There is, however, a fairly definite boundary line between the 
* Plates 14—18, containing figs. 5—14, represent the cell lamination of the cortex in 
typical areas of the lemur’s brain. The drawings were made with the camera lucida, the 
magnification being 120 diameters. A description of these areas is given in the text. 
