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PLATE I.—continued.

Figure 19.—The posterior part of the hemisphere, represented in Figure 14, removed hy coronal section. The intraventricular
infoldings produced by the calcarine (c.) and external calcarine (e. c.) fissures are seen.

Figure 20.—The posterior part of the right cerebral hemisphere of Cercopithecus griseoviridis, removed by coronal section.
The effect produced upon the posterior horn of the lateral ventricle (v.) by the calcarine (c.) and external calcarine fissures
Is seen.

Figure 21.—Left cerebral hemisphere viewed from the front. Period of development, middle of fifth month :—*., fossa
Sylvia ; 1 and 2, primitive polar gyri (vide 102 of the text) ; 3, the uncus.

Figure 22.—Eight cerebral hemisphere in the sixth month of development:—1 and 2, primitive polar gyri.

Figure 23.—Left cerebral hemisphere in the fifth month of development:—1 and 2, primitive polar gyri; 3. the uncus.

Figures 24 and 25.—The two cerebral hemispheres from a foetus which had reached the latter part of the sixth month of
development:—t., parallel sulcus ; o., the first appearance of the frontal operculum (pars triangularis).

Figure 26.—The inner face of the hemisphere represented in Figure 24 :—c. »»., calloso-marginal sulcus; p. o., parietooccipital
fissure conjoined with the "stem" of the calcarine fissure; c.1 and c.3, two punctiform depressions representing
the earliest condition of the two parts of the secondary posterior part of the calcarine fissure.

[N.B.—In this figure, c.1 should have been lettered c.3 to bring it into correspondence with the lettering in the other
figures.]

Figures 28 and 29.—Two views of the hinder end of a cerebrum obtained from a foetus in the early part of the seventh
month.

In Figure 29 the mesial face of the hemisphere is represented. The parieto-occipital fissure (p. o.) joined to the
"stem" of the calcarine fissure (c.1) is exhibited. The two shallow secondary sulci (c.2 and c.3), which afterwards unite to
form the posterior part of the calcarine fissure, are also seen.

In Figure 28 the outer face of the same portion of this hemisphere is exhibited, and the outer wall of the ventricular
cavity has been removed. The intraventricular infolding corresponding to the united parieto-occipital and anterior calcarine
fissures is observed (p. o.). In this case the parieto-occipital fissure forms a very decided infolding.

Figures 27 and 30.—Two views of the hinder end of a cerebrum obtained from a foetus in the early part of the seventh
month. Figure 30, mesial surface; Figure 27, outer surface with the outer wall of the ventricular cavity removed.
Lettering the same as in Figures 28 and 29. In this case the parieto-occipital fissure produces no intraventricular elevation;
the calcar avis is entirely formed by the " stem " or the anterior complete part of the calcarine fissure. (Vide p. 51 of the text.)

Figure 31.—Outer surface of a cerebral hemisphere in the early part of the seventh month of development; considerably
enlarged. The specimen is in the Biological Museum of the University of Oxford. The photograph was obtained from
Professor Victor Horsley :—t.1, parallel sulcus ; p. c. i., in all probability this sulcus is the inferior frontal furrow, or the
inferior frontal furrow in conjunction with the sulcus praecentralis inferior.

Figure 32.—Coronal section through the hinder end of a cerebral hemisphere in the seventh month of development, to
show the relation of the " stem " of the calcarine fissure (c.) to the ventricular cavity (v.).

Figure 33.—Foetal hemisphere well on in the eighth month of development. The temporal operculum has been removed.
The three radial furrows on the island of Roil—the sulcus proscentralis 1, the sulcus centralis 2, and the sulcus postcentral 3
are exhibited :—»'. t., inferior transverse furrow of the fissure of Rolando; F. P., fronto-parietal operculum; 0., orbital
operculum. The pars triangularis or frontal operculum is well seen, but it is not lettered.

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