46 
MR. W. BEVAN LEWIS ON THE COMPARATIVE 
At E, and still more at F, the dense confluent groups re-appear, although the tendency 
to thin out into discrete clusters shows itself towards the crucial sulcus. A gradual 
reduction in the dimensions of these cells is noticed towards F, so that at the com¬ 
mencement of the crucial sulcus they average but 28p,Xl7p,. Further forwards at 
A, dense groups appear on the internal aspect of the lobe just where it becomes super¬ 
ficial, but between this and the crucial sulcus the cells are scattered in distant groups, 
and average in size 37/rX 16/x. These densely-grouped confluent nests may be traced 
down along the whole internal aspect of the anterior arc of the limbic lobe as far 
forwards as the sub-frontal sulcus. In the divisions marked A G great fusiform cells 
are frequently met with measuring 55 p, longXlSp, in diameter, or 69 y X lip. In 
entering thus somewhat minutely into the details of examination of an important 
region of the cortex, I have been influenced by the desire of pointing out what may 
prove a significant fact: that these groups of ganglionic cells do not form an equably 
distributed layer, but are associated in dense masses towards various centres with 
intervening tracts formed by distant or discrete cell groupings. The remaining portion 
of the convolution of the corpus callosum, viz. : that part lying beneath the sub-parietal 
sulcus and limited posteriorly by the retro-limbic annectant, presents us with the most 
perfect example of the six-laminated cortex and solitary arrangement of ganglionic cells. 
The band of angular or pyramidal elements separating the third layer from the 
ganglionic is both deep and dense. 
2. Frontal lobe. —The extreme tip of the hemisphere anteriorly constituting the 
frontal lobe presents us with the nested arrangement of cells, the nests being in 
the ascending frontal convolution thinly supplied with cells and distant in their 
grouping, whilst throughout the ascending parietal gyrus the nests are formed of 
densely-congregated cells. These rich nests are, however, invariably discrete and even 
distant. The inner aspect of the frontal lobe, limited behind by the sub-frontal sulcus, 
has numerous cell groups which form, however, but ill-defined nests. Throughout 
the whole extent of the frontal lobe no coalescence of groups or confluent nests were 
observed. 
3. Parietal lobe. —The four convolutions constituting this lobe are by no means 
identical in structure throughout. The convolutions below the inter-parietal fissure 
will first engage our attention. The first or Sylvian convolution is usually blended 
with the second parietal in front of the fissure of Sylvius ; a few faint markings indi¬ 
cating their line of union. Throughout these convolutions the general arrangement of 
ganglionic cells is in shallow, ill-formed nests, poor in cells, and the nests discrete and 
often distant. The richer aggregation of cells occurs along what corresponds to the 
second parietal gyrus bordering upon the inter-parietal fissure, and they thin out into 
distant nests towards the Sylvian fissure. The groups of cells are dense and almost 
con fluent in the divisions ABC, fig. 2, of the second parietal convolution, as also they 
are throughout the whole extent of the first and second parietal convolutions at F. 
Still further back at G we find both gyri possess well-formed distinct nests of from 
