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De. Cunningham—Surface Anatomy of the Primate Cerebrum. 267

Heive" has also recognized the interrupted form of the sulcus. He says:
" Mais sur un grand nombre de cerveaux, et non tous parmi les plus
simples, la face convexe de F2 (i. e. the middle frontal convolution) est par-
courue en son milieu par une sexie d'incisures et de sillons isoles, quelque-
fois continus, qui manifestement la d^doublent sur une partie plus ou moins
notable de sa longeur en deux plis distinct."*

The terminal cross-piece which skirts the superciliary margin of the
hemisphere is very constant, and has been described by Wernicke as a
separate furrow, under the name of the fronto-marginal sulcus. He states,
that " sie ist quer gegen den Langsverlauf der Windungen gestellt und
schneidet oberhalb der Orbitalkante des Stirnlappens nach rechts und
links in die zweite und dritte Stirnwindung ein."f It presents the
appearance of being a terminal bifurcation of the sulcus frontalis medius
in which the two limbs are widely spread out from each other (figs. 53 and
59, pp. 248 and 262, w.). In a large number of cases it is partially cut
off from the stem by a deep bridging gyrus. This may rise to the surface,
and then the fronto-marginal furrow becomes an independent sulcus.

Eberstaller has rightly called attention to the fact that the outer limb
of this terminal bifurcation of the middle frontal sulcus is frequently partially
separated from the main stem of the furrow, and also from the inner
limb, by a deep bridging gyrus. I have noted this interruption in 20*7 per
cent, of the hemispheres examined. This breach of continuity has led
Eberstaller to consider that the inner limb of the bifurcation of the main
stem is the true continuation of the sagittal part of the furrow. I hardly
agree with him in this, seeing that it also may be partially detached
(7*2 per cent.). Further, in figure 60 (p. 268), which shows the furrows
of the frontal lobe in a foetal cerebrum, it will be seen that the terminal part
of the sulcus frontalis medius turns outwards, and there is as yet no sign
of the inner limb of the bifurcation.

In many cases the hinder end of the sulcus frontalis medius is connected
with the sulcus frontalis primus (Eberstaller states in 44 per

* La circonYolution de Broca. Paris, 1888, p. 70.

f "Das Urwindungssj-stem des mensehlichen Gehirns," Archiv fur Psychiatrie, &c,
Band vi., Heft 1, 1875, p. 304.

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