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Accepting the latter, I shall examine whether the sulcus lunatus, 
described by Entior Smita, answers the requirements which are due 
to an ape fissure, it being moreover accepted as granted, that not 
every sulcus on the occipital pole of the brain can be called an ape 
fissure. It will therefore need some characteristics, by which it can 
be differentiated from other sulci. 
This is the more necessary, as it is known to us, that the sulei on 
the lobus occipitalis show such a varying picture that to distinguish 
the most familiar fissurae already gives rise to difficulty. Thus 
WaLbprvER wrote: “Es gelang Rerzius ebenso wenig wie seinen 
Vorgängern, eine typische Anordnung der Furchen und Windungen 
am Hinterlappen des Grosshirns nachzuweisen: derselbe wird also 
noch bis auf weiteres die Crux der Hirnanatomie nach dieser Seite 
hin bleiben”. 
It is also known that at the occipital pole through the transvers- 
ally and obliquely running sulci one can find, gyri, which possess 
the likeness to an operculum. This “Halbringform” is described a.o. 
by Rerstus on page 186, where the fissura calcarine continues on 
the lateral brainmantle, forming a “nach vorn-oben vorhängendes 
operculum.” 
These, let me call them pseudo-opercula, therefore do not develop 
by overgrowth, but by a confluence, or more by an oblique course 
of ordinary sulci. 
We could compare it with a ball, of which the half of a super- 
ficial segment is cut in, forming thus a thing that looks like a 
fictitious operculum, a ““Klappdecke”. 
The presence therefore of a thing that in man resembles an 
operculum, does not give a right to speak of an ape-fissure. This 
too Errior SmirH*) admits, when he writes on page 448 “...especially 
the suleus oce. transversus may have a caudal opercular lip, which 
simulates the true stria-bearing occipital operculum”. 
Where this mighty means to determine an ape-fissure, falls away, 
there only a few characteristics remain, which can be helpful in 
identifying this sulcus. 
The first is the pushing inwards or overgrowing of sulci, which 
under normal circumstances remain on the surface. 
It speaks for itself that in connection with the previous question, 
it is not always very easy to make out whether a sulcus is pushed 
to the depth either through overgrowth of an adjoining part, or 
whether the arisen relation is the result of a confluence which is 
so often seen on the brain surface. Moreover it often happens that 
sulei which for the greater part are lying on the surface, can be 
