On the Brain | Page 6

in this series lies between Hapale and Lemur, and that this break
is considerably greater than that between any other two terms of that

series. Professor Bischoff ignores the fact that long before he wrote,
Gratiolet had suggested the separation of the Lemurs from the other
Primates on the very ground of the difference in their cerebral
characters; and that Professor Flower had made the following
observations in the course of his description of the brain of the Javan
Loris: (75. 'Transactions of the Zoological Society,' vol. v. 1862.)
"And it is especially remarkable that, in the development of the
posterior lobes, there is no approximation to the Lemurine, short
hemisphered brain, in those monkeys which are commonly supposed to
approach this family in other respects, viz. the lower members of the
Platyrrhine group."
So far as the structure of the adult brain is concerned, then, the very
considerable additions to our knowledge, which have been made by the
researches of so many investigators, during the past ten years, fully
justify the statement which I made in 1863. But it has been said, that,
admitting the similarity between the adult brains of man and apes, they
are nevertheless, in reality, widely different, because they exhibit
fundamental differences in the mode of their development. No one
would be more ready than I to admit the force of this argument, if such
fundamental differences of development really exist. But I deny that
they do exist. On the contrary, there is a fundamental agreement in the
development of the brain in men and apes.
Gratiolet originated the statement that there is a fundamental difference
in the development of the brains of apes and that of man--consisting in
this; that, in the apes, the sulci which first make their appearance are
situated on the posterior region of the cerebral hemispheres, while, in
the human foetus, the sulci first become visible on the frontal lobes. (76.
"Chez tous les singes, les plis posterieurs se developpent les premiers;
les plis anterieurs se developpent plus tard, aussi la vertebre occipitale
et la parietale sont-elles relativement tres-grandes chez le foetus.
L'Homme presente une exception remarquable quant a l'epoque de
l'apparition des plis frontaux, qui sont les premiers indiques; mais le
developpement general du lobe frontal, envisage seulement par rapport
a son volume, suit les memes lois que dans les singes:" Gratiolet,

'Memoire sur les plis cerebres de l'Homme et des Primateaux,' p. 39,
Tab. iv, fig. 3.)
This general statement is based upon two observations, the one of a
Gibbon almost ready to be born, in which the posterior gyri were "well
developed," while those of the frontal lobes were "hardly indicated" (77.
Gratiolet's words are (loc. cit. p. 39): "Dans le foetus dont il s'agit les
plis cerebraux posterieurs sont bien developpes, tandis que les plis du
lobe frontal sont a peine indiques." The figure, however (Pl. iv, fig. 3),
shews the fissure of Rolando, and one of the frontal sulci plainly
enough. Nevertheless, M. Alix, in his 'Notice sur les travaux
anthropologiques de Gratiolet' ('Mem. de la Societe d'Anthropologie de
Paris,' 1868, page 32), writes thus: "Gratiolet a eu entre les mains le
cerveau d'un foetus de Gibbon, singe eminemment superieur, et
tellement rapproche de l'orang, que des naturalistes tres-competents
l'ont range parmi les anthropoides. M. Huxley, par exemple, n'hesite
pas sur ce point. Eh bien, c'est sur le cerveau d'un foetus de Gibbon que
Gratiolet a vu LES CIRCONVOLUTIONS DU LOBE
TEMPORO-SPHENOIDAL DEJA DEVELOPPEES LORSQU'IL
N'EXISTENT PAS ENCORE DE PLIS SUR LE LOBE FRONTAL. Il
etait donc bien autorise a dire que, chez l'homme les circonvolutions
apparaissent d'a en w, tandis que chez les singes elles se developpent
d'w en a."), and the other of a human foetus at the 22nd or 23rd week of
uterogestation, in which Gratiolet notes that the insula was uncovered,
but that nevertheless "des incisures sement de lobe anterieur, une
scissure peu profonde indique la separation du lobe occipital,
tres-reduit, d'ailleurs des cette epoque. Le reste de la surface cerebrale
est encore absolument lisse."
Three views of this brain are given in Plate II, figs. 1, 2, 3, of the work
cited, shewing the upper, lateral and inferior views of the hemispheres,
but not the inner view. It is worthy of note that the figure by no means
bears out Gratiolet's description, inasmuch as the fissure
(antero-temporal) on the posterior half of the face of the hemisphere is
more marked than any of those vaguely indicated in the anterior half. If
the figure is correct, it in no way justifies Gratiolet's conclusion: "Il y a
donc entre ces cerveaux [those of a Callithrix and of a Gibbon] et celui

du foetus humain une difference fondamental. Chez celui-ci, longtemps
avant que les plis temporaux apparaissent, les plis frontaux,
ESSAYENT d'exister."
Since Gratiolet's time, however,