50 
MR. W. BEVAN LEWIS ON THE COMPARATIVE 
stratum deep. Passing now to the subject of regional distribution of the different types 
of lamination, and the diverse arrangements of the ganglionic series, we shall rapidly 
glance at each individual lobe. 
Regional Distribution. 
Great limbic lobe. —The anterior half of the superior arc of this lobe, fig. 4, is 
distinctly five-laminated, whilst the ganglionic series of cells is arranged in clusters 
throughout the whole extent of this lobe as far back as the retro-limbic annectant. 
From the commencement of the crucial sulcus the nested arrangement of these cells 
becomes a more marked feature the further forward our examination extends, so that 
in the neighbourhood of the fronto-limbic sulcus the nests are large and richly 
Eio'. 4. 
crowded with ganglion cells. The groupings also in this situation are frequently 
confluent. Although the nested grouping of this formation is maintained throughout 
the superior arc of this lobe, a great dissimilarity is seen between sections taken near 
the posterior extremity of the corpus callosum and those from regions anterior to its 
genu. The posterior half of this upper arc differs however not only in the mode of 
grouping of its elementary constituents—a fundamental divergence is observed in its 
lamination. Beneath the whole extent of the sub-parietal sulcus the limbic lobe is 
found to be six-laminated (Plate 7). This change in the type of cortical stratification 
is assumed at fig. 4 ('"), a little posterior to the point where the sub-parietal sulcus 
becomes superficial on the surface of the hemisphere, and is continued as the crucial 
sulcus. The intercalated series of small angular cells is first observed therefore where 
the limbic lobe comes close in contiguity with the sagittal gyrus of the parietal lobe 
at the origin of the crucial sulcus. A similar disposition is maintained in the lami¬ 
nation of the limbic lobe in the Pig, as we have already stated above. From this 
point the six-laminated cortex is spread downwards and backwards over the whole 
posterior portion of the superior limbic arc. The intercalated series of small angular 
elements becomes more and more richly developed towards the retro-limbic annectant, 
where it forms a dense and deep stratum, which readily characterises this region as 
wholly differing in important features from realms anterior to the crucial sulcus. 
