Freiburger historische Bestände - digital

Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 293

The sulcus frontalis superior is present in the form of a long continuous
furrow, free from interrupting deep annectant gyri. The prsecen-
tralis superior (p.c.s.) is well marked; but, as in the case of the right
hemisphere, it is difficult to decide whether the furrow lettered " fl" is the
lower piece of this sulcus, or a sulcus prsecentralis medius.

The sulcus prsecentralis inferior (p. c. i.) is very similar to the corresponding
furrow in the opposite hemisphere, but the ramus horizontalis (h)
is, if anything, more obliquely placed.

The sulcus frontalis medius (/. m.) is broken up into three pieces. The
hindermost of these is superficially connected (as in the right hemisphere)
with the front limb of the ramus horizontalis of the inferior prsecentral
sulcus. The second or intermediate piece takes an oblique course towards
the mesial border. It is a clean-cut deep furrow ; and I am inclined to
believe that anteriorly it has entered into connexion with and completely
absorbed a detached part of the sulcus frontalis superior. It is right to
state, however, that there is no deep annectant gyrus present to mark the
point of junction. The terminal piece thus forsaken by the intermediate
part has entered into an abnormal connexion with the inferior frontal
sulcus. At least that is the light in which I am inclined to regard the
bifurcated furrow which lies front of the inferior frontal sulcus. A high,
deep annectant gyrus indicates the point of union.

The inferior frontal sulcus (/.2) is arranged in the same manner as the
corresponding furrow on the opposite hemisphere, with two exceptions :
(1) it enters into complete union behind with the vertical stem of the
inferior prsecentral sulcus; (2) it presents, as we have noted, an abnormal
but superficial connexion in front with what appears to be the terminal part
of the sulcus frontalis medius.

A third chimpanzee hemisphere in my possession exhibits an arrangement
of the furrows on the frontal lobe very similar to that just described.
The sulcus frontalis medius, however, is more distinct, and its terminal
part is not connected with the inferior frontal sulcus. All the sagittal
furrows are more or less oblique, and tend towards the mesial border by
their anterior extremities.

In a fourth chimpanzee hemisphere I can see no trace of a sulcus