44 
MR. W. BE VAN" LEWIS ON THE COMPARATIVE 
3. Dimensions of cells. —The largest cells are found anterior to the crucial sulcus hr 
the antero-superior portion of the great limbic lobe, where that lobe becomes super¬ 
ficial on the hemisphere, figs. 1 and 2 (4). Next to them in point of size are the 
ganglionic cells of the anterior portion of the parietal convolution immediately external 
to the crucial sulcus. In the exposed portion of the limbic lobe above referred to, 
the cells attain the dimensions of 48/x in length by 17 g in breadth, their nucleus 
measuring 15/x long. Such are the dimensions in the middle third of this region, 
fig. 2 (B C). Towards the frontal extremity of the hemisphere near the fissure of 
Rolando, fig. 2 (.9) they decrease to 3 7 g X 16p, (nucleus 11/x), whilst posteriorly at 
the commencement of the crucial sulcus the}?- average but 25/x X 1 9/jl. The variations 
observed in the dimensions of these cells will be further dealt with in our remarks 
upon regional distribution, and will also be found in a tabulated form at the end of 
this article. 
Regional Distribution. 
That portion of the antero-superior arc of the great limbic lobe or convolution of the 
corpus callosum, which becomes in the Pig and other Mammals superficial on the 
upper aspect of the hemisphere, and which in this animal bounds the anterior half of 
the longitudinal fissure, is par excellence the region which exhibits the highest develop¬ 
ment attained by the ganglionic series of cells. From the commencement of the 
crucial sulcus where this lobe becomes superficial to its termination anteriorly, the five- 
laminated cortex and nested arrangement of the fourth layer of cells is maintained 
throughout. Local variations in the distribution of the ganglionic cells occur markedly 
in this lobe, and will require separate notice further on. For the present it is necessary 
that we trace the regions over which this characteristic formation is spread. The 
Eig. 3. 
extreme anterior tip of the hemisphere participates in this formation, both convolutions 
bordering upon the fissure of Rolando exhibiting a five-laminated cortex and distinct 
clustered cells in the fourth layer. The same fundamental type of structure can be 
traced along the whole course of the lowest parietal convolutions (first and second), 
from their union with the ascending parietal (post-Rolandique, Broca) towards and 
