Freiburger historische Bestände - digital

2

Cunningham Memoirs.

Amongst the " Totalfalten" His* includes the fossa Sylvii, but
Mihalkovicsf rightly denies it a place in this category. The majority of
anatomists, however, agree with the former observer. Thus Hertwig, in
the third edition of his treatise on Embryology^ distinctly gives expression
to that view.

The projection into the hemisphere cavity which corresponds to the
fossa Sylvii (viz. the corpus striatum) is not formed by an infolding of the
mantle wall, but as an elevation which rises on the floor of the prosencephalon
. The surface area corresponding to this internal projection does
not keep pace with the mantle as the latter grows around it, and in
consequence the Sylvian depression makes its appearance. The development
of this fissure then is peculiar, and altogether different from that of
the ""Totalfalten " of His.

Under ordinary circumstances, and under normal conditions, none of
the complete fissures which appear on the outer face of the embryonic
hemisphere are retained as permanent sulci. Later on we shall have
occasion to mention two which apparently persist in the ape. The
corresponding fissures in man, however, are of a transitory nature.

On the inner or mesial face of the hemisphere the conditions of
growth are different. These are more favourable to the appearance of
such infoldings, and also more favourable to their retention. It is here,
therefore, that we find the complete fissures which are preserved in the
adult brain. These are:—(1) the choroid fissure; (2) a portion of the
arcuate fissure; (3) and under certain conditions the parieto-occipital, with
the fore-part of the calcarine fissure.

II. Choroid and Arcuate Fissures.—In his recent work upon the
development of the human fore-brain, His gives an excellent account of
the early development of these fissures. They appear at a very early
period on the inner surface of the hemisphere. His figures the cerebrum

* Unsere Korperform, Neunter Brief, p. 116.
f Entwicklungsgeschichte des Gehirns, 1877.

\ Traite d'Embryologie ou Histoire du Developpement de 1'Homme et des Yertebres, par Oscar
Hertwig (traduit sur la troisieme edition allemande par Charles Julin, Paris, 1891), p. 395.