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268

Cunningham Memoirs.

cent.). It is usually brought about by the transverse portion which
is placed in relation to its hinder end, and it does not necessarily bring
the two sulci into a direct line with each other. But even in cases
where this occurs the union is generally not complete, but is interrupted
by the presence of a deep bridging gyrus (fig. 59, p. 262). In rare
instances an absolute and uninterrupted continuity may be established
(fig. 57, p. 259). In these cases the sulcus frontalis medius is removed from
its normal connexions. It lies nearer the mesial border of the hemisnhere,
and the ground which it usually occupies is traversed by two or three
shallow transverse sulci (figs. 57 and 59, pp. 259 and 262, /. m.) which lie
in series with each other.

Fig. 60.—Profile view of a cerebrum from a male foetus in the latter part of the seventh month of
development. Drawn by the American apparatus for tracing orthogonal projections of
the skull. The dotted lines indicate the position of the deep bridging gyri.

r.

Fissure of Eolando.

s.2 .

. Ascending anterior limb of Sylvian

p. c. s.

Sulcus praecentralis superior.



fissure.

a. .

Sulcus praecentralis marginalis.

s\ .

. Anterior horizontal limb of Sylvian

h. .

Horizontal limb of the sulcus praecentralis



fissure.



inferior.

f-1 ■

. Sulcus frontalis primus.

p. c. i.

Vertical limb of the sulcus praecentralis

f. VI.

. Sulcus frontalis medius.



inferior.

/•2 •

. Sulcus frontalis secundus.

VIII. Sulcus Frontalis Mesialis.—Broca has called attention to the
fact, that the convex external surface of the superior frontal convolution is
never simple. il It is always more or less subdivided by furrows directed