Freiburger historische Bestände - digital

212

Cunningham Memoirs.

the apes would alike appear to indicate this variety as the typical one, but
certainly it is not the most common. It was discovered in 27 of the 127
hemispheres examined.

63 Adult hemispheres, . . . , . . 19*1 per cent.

8 Negro hemispheres, ...... 25 ,,

19 Children's hemispheres . . . . . 26*4
17 Full-time foetal hemispheres, . . . . 35-3

20 Eighth-month foetal hemispheres, . . . 10 ,,

The percentages which are given above, in a measure justify the statement
which I have previously made in regard to the period at which the
sulcus postcentralis superior joins the sulcus postcentralis inferior. In
many cases it is evident that this union is delayed until after birth (vide
19-1 per cent, for the adult, 264 for the child, and 35*3 for the full-time

Fig. 40.—Left Hemisphere of a new-born Male Child. It shows the typical condition

of the intraparietal sulcus.

foetus). The low percentage for this variety in the eighth-month foetus
is difficult to explain, and is only partially accounted for by the high
percentage for Variety I. (in which the sulcus postcentralis superior is
also separate) in hemispheres at the same period of development.

Sernoff * has found this condition of the intraparietal sulcus in the adult
Russian brain less frequently than I have noticed it in the Irish cerebrum.

Vaeiety III.—Postcentral sulci confluent; ramus horizontalis separate.—A
well-marked example of this variety of the fissure is represented in figure 41.
At first sight the hemisphere appears to be traversed by two fissures of

* Individualniye tipy mozgovykh izvilin u tcheloveka. Moscow, 1877, p. 34.