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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 9

account of the fissures in question, and has added considerably to our
knowledge regarding them.

It is somewhat curious that Bischoff, writing as late as 1868, should
have cast doubt upon the reality of the transitory furrows. He asserts
that all previous observations in this direction are founded on an error, and
that the fissures in question are produced artificially by the action of the
alcohol in which the brains have been immersed. He further maintains
that in specimens treated with chloride of zinc the surface of the hemisphere
remains perfectly smooth up to the time of the appearance of the permanent
sulci. To quote his own words:—"Die weiche und sehr wasserhaltige
Beschaffenheit junger Gehirne, vor Allem die verhaltnissmassig sehr
grossen Hohlraume, weiche die einzelnen Hirnabtheilungen umschliessen,
bedingen bei dem Einbringen der Embryonen in Weingeist, welches zur
Herausnahme der Gehirne unvermeidlich war, ein starkes Schrumpfen und
Zusammenfallen und besonders an den Hemispharen eine Faltenbildung,
weiche etwas Regelmassiges zu haben scheint. Allein sie sind nur Kunst-
produkt."*

Ecker disposes of this objection by the statement that he has observed
the transitory furrows in the brain of a third-month embryo which was
examined in the fresh state. I can verify this statement, as I have
frequently seen the fissures under similar conditions, and moreover I have
chiefly studied them in brains prepared by the chloride of zinc method.
At the same time I fully agree with both Ecker and His in considering
that some care must be exercised in distinguishing between true and
artificial folds in the thin wall of the cerebral wall. The latter author, in
his recent work upon the forebrain, very properly remarks:—"In human
material one meets with the special difficulty that the thin-walled hemisphere
vesicle frequently, through external accidents, becomes folded
(through pressure upon the head in birth or in the preparation of the
embryo, or through shrinkage in consequence of defective preservation),
and that the accidental folds thus produced are combined with the natural
folds. With some circumspection in the choice of material one can

* Die Grosshixnwindxtngen dcs Mensclien, &e. &c, Abh. d. 11. CI. d. k. bayer. Akad. d.
Wiss. Ed. x., Abth. 11., p. 446.

EOYAX ERISH ACADEMY.—CUNNINGHAM MEMOLES, NO. VH. [2]