STRUCTURE OF THE CORTEX CEREBRI. 
39 
Cat, Dog, and allied animals. In these latter regions the ganglionic cells are clustered 
one above the other, occupying oval areas forming the well-known “nests” of Betz, 
and usually separated by short intervals from one another (Plate 7). The second arrange¬ 
ment, however, reminds one of the characters exhibited by this series of cells at the 
bottom of a sulcus. Here (in the sulcus) we find solitary cells at great comparative 
distances apart, arranged irregularly along the floor of the sulcus, forming in vertical 
sections a well-marked linear series (Plate 7). Not unfrequently two cells lie side by 
side, but no groups of such elements are discoverable in these localities ; hence the 
depth of this layer is far less than the same layer at the summit or side of a convolu¬ 
tion. Vertical sections will therefore show at the summit of the gyrus deep oval groups 
of cells, contrasted with a simple streak of solitary and distant cells at the bottom of 
the sulcus. In general terms, it may be said that the typical arrangement of the gan¬ 
glionic series, at the base of a sulcus, is identical with the formation of the same layer 
over a very extensive area of the vault. When in examining vertical sections of the 
cortex we find the grouped cells give place at the summit and sides of a convolution to a 
shallow streak of distant cells, arranged as solitary cells or in twos or threes at most, we 
may assure ourselves we have passed from the region which Perrier considers impressed 
with motor endowments, and have reached a territory possessing an equally charac¬ 
teristic formation. Further, the transition from the grouped arrangement into the 
solitary or laminar band here referred to resembles what is observed at the sides and 
base of a sulcus in the motor area. The groups, from being closely aggregated, become 
more distant and discrete; the groups themselves become shallower, include fewer 
cells, until one or two elements alone reappear at great distances apart, and charac¬ 
terise the region furnished with the solitary or laminar type. I do not mean to infer 
that the base of a sulcus in the motor area furnishes us with a lamination identical in 
its characters with that of non-motor realms. The distinctions are as follows : in the 
region just alluded to as possessing the laminar arrangement of ganglionic cells there 
is superimposed on it a distinct layer of small pyramidal and angular cells, whilst the 
horizontal distribution of spindle cells never occurs except at the base of a sulcus. 
To summarise, then, in a few words, we have two regions of the vault characterised by 
two very distinct types of lamination :— 
A. The five-laminated type with its grouped ganglionic cells, exhibiting a laminar 
arrangement at the sulcus only. 
B. The six-laminated type, with the solitary laminar arrangement of the sulcus 
generally distributed over the summit and sides of the gyrus ; and the introduction of 
a layer of small pyramidal elements immediately above the ganglionic group. 
Transition realms .—Every intermediate state is clearly discernible betwixt these two 
types of lamination in neighbourhoods where they approach each other and blend. Thus, 
in studying the passage of a five- into a six-laminated region, we meet with territories 
where the five-laminated cortex presents us with very small ganglionic cells still arranged 
in nests, and forming but pigmy representatives of those larger groups believed to be 
