M. G. Schlapp _ 265 
Dog as 2.210 : 1.690 
Monkey 2.340 : 1.590 
Man 3.510 : 1/820 
It is evident from these figures that this difference between the motor 
and sensory cortex is least in the dog and most in man. 
In the pteropus, the large cells are distributed over a relatively large 
cortical area in the anterior portion of the hemisphere on its lateral as 
well as on its medial surface. They are situated in the fourth layer of 
the five layer type. For the reason that relatively large cells are found 
in the pteropus in such large numbers, and are spread over so large an 
area, I am inclined to doubt that these really represent the motor cells 
only. These cells, being in a parapyknomorphic state, do not differ 
from the other pyramidal cells in the same region, whereas the motor or 
large pyramidal cells in higher animals are in a pyknomorphic state, 
compared with the parapyknomorphic state of the smaller pyramidal 
cells in the same region. 
In the cat and the dog, these cells lie in a limited area surrounding 
the fissura cruciata. 
In the monkey, they lie in the well defined anterior central gyrus, but 
isolated cells are still found in the posterior central gyrus. They do 
not, however, reach as far ventralward in the posterior central gyrus as 
the stem of the fissure of Sylvius, but only as far as the lower extremity 
of the central sulcus of Rolando, which is shorter comparatively in the 
monkey than in man. The large pyramidal cells in the posterior central 
gyrus are not so large as the same cells in the anterior central. 
In the human cortex, the large pyramidal cells are found in the ante- 
rior central gyrus. Both in size and in numbers they reach their high- 
est point of development in the dorsal portion of the anterior central, 
but diminish in both respects as they approach the ventral extremity of 
this gyrus. Anteriorly from the anterior central gyrus they oceur only 
in small numbers in the posterior extremity of the upper and middle 
frontal gyri. 
On examination of the motor area, with a low power lens (a. a. Zeiss), 
one observes the pecular fact that in lower animals the large pyramidal 
cells are crowded closely together and presumably on that account occupy 
a limited area, while in man the cells are more scattered and cover a 
comparatively larger area of the cortex. Posteriorly from the anterior 
central gyrus, the boundary being formed by the central sulcus (fissure 
of Rolando), the motor type passes abruptly into the seven layer type, 
while toward the frontal lobe the transition into the seven layer type 
is gradual. This latter type in the frontal lobe resembles the parietal 
