1908.] Cell Lamunation of Cerebral Cortex of the Lemur. 497 
above or among the granules, and the granules form a fairly well-marked 
line. 
The cells which correspond in position to the Betz cells in “ Motor A” are 
not conspicuous either in size, staining, or number. But a somewhat 
scattered line of cells can be seen measuring about 25 uw by 15m which are 
Betz-like in shape, having many branched processes and Nissl granules. 
From the facts that the movements of the head and eyes, mouth, closure of 
opposite eye, side of face and tongue, and pricking of ears have been 
obtained by stimulation of this area, and that the cells here described are 
present, it may be inferred that this area is motor in function, although it 
differs considerably from the typical motor cortex in the characteristics 
mentioned above. The presence of stellate cells and granules points to 
a sensory type. This area is probably a sensori-motor area which is experi- 
mentally excitable, giving rise to definite movements; and corresponding to 
another definite sensori-motor area—the calcarine visual cortex, which, in 
the ape, gives rise to definite movements on stimulation. But for reasons 
which have been given in Addendum (p. 505), the visual cortex has not 
been experimentally proved to be excitable in the lemur. 
Frontal Area. 
00004 
Extent and Boundaries: Frontal A |\g9292|.—This area forms a band about 
avgcand 
1 mm. in width across the dorso-mesial surface from the sulcus rectus to the 
intercalary sulcus. It is bounded anteriorly by “Frontal B”; posteriorly it 
extends nearly to the level of the end of the sulcus rectus, and there 
merges into an intermediate area which lies between this type and the motor 
area. 
Frontal B.—Type “Frontal B” covers the anterior pole of the hemi- 
sphere, and extends: Posteriorly, on to the dorsal and mesial surfaces 
for about 2 mm. backwards, being bounded by “Frontal A;” on the mesial 
surface to the intercalary sulcus, and, further forward, to an imaginary line 
continuous with this sulcus to the pole; inferiorly, to the orbital and 
fronto-orbital sulci.* 
Characteristics: Frontal A.—The cortex is about 2 mm. deep, the molecular 
* A comparison with the brains of the primates, described by Campbell, suggests that 
an “orbital” type of cortex would be found in this position. We have not, however, 
found sufficient histological evidence to justify mapping out a separate type here, although 
it may be noted that in sections of so small a brain the cortical lamination of this region 
is often distorted, owing to the sections being necessarily cut through the walls of the 
short, branched orbital sulcus. It is thus difficult to make exact observations on this part 
of the cortex. 
ZB 2 
