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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 139

We must endeavour therefore to ascertain:—

1. The relative position of the Sylvian fissure with reference to the
squamo-parietal suture.

2. The relative position of the fissure with reference to the mesial and
infero-lateral borders of the hemisphere.

Further, in making' our measurements it is essential in every case to
follow precisely the same line. The following is the plan which I have
adopted:—I have taken the longest antero-posterior axis of the cerebrum
as a base-line, and from this I have let drop a perpendicular which cuts
through the inferior end of the ascending parietal convolution. Such a line
when carried upwards usually cuts the mesial border of the hemisphere
immediately in front of the ascending frontal convolution, whilst below, if
prolonged beyond the brain, it would reach the anterior border of the
external auditory meatus. All my measurements between points on the
surface of the brain have been made along this vertical line. In estimating
the distance between the squamo-parietal suture and the Sylvian
fissure, however, I found it impossible to adhere rigorously to such a
line. In this instance, therefore, I have always measured the distance of
the fissure from the highest point of the suture.

Where the measurements were made upon hemispheres removed from
the cranial cavity use was made of the sheet of glass already referred to in
connexion with the determination of the S}dvian angle. The cerebral
hemisphere was placed with its mesial surface downwards on the glass, and
adjusted so that the longitudinal line corresponded with its anteroposterior
axis, and the vertical line cut the mesial border of the hemisphere
just in front of the ascending frontal convolution. The outer surface of
the specimen was then measured in the direction of the latter line.

The measurements were made with the tape. We shall distinguish the
entire measurement from the mesial to the infero-lateral margin of the
hemisphere measured along the vertical line indicated as the parieto-temporal
depth; the distance from the mesial border of the hemisphere to the
fissure we shall term the parietal depth; and the measurement from the

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