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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 151

Adults.

Let us first deal with the adults. Of these I have studied six, the heads
of which, with the brain exposed in situ, were all modelled. Five of the
models in question are figured in Plates vn. and viii. (figs. 12, 13, 15,
16, 17); but the models were not well adapted for this part of the inquiry.
The bars of bone which were left in the lines of the sutures concealed too
much of the area and often hid the anterior limbs completely or in part.
My observations have therefore been made directly on the specimens after
the moulds were prepared and after the removal of portions of the bony
bars. In some cases it was necessary to remove the cerebrum after fixing
the lines of the sutures by means of pins introduced into the brain.

In dealing with the heads of adults it is often difficult to establish the
precise coronal line in its lower part, because it is here that obliteration of
the suture is so apt to occur. This is all the more unfortunate, seeing that
it is in this part of the suture that the overlapping squamous process of the
parietal bone leads to changes in the direction of the coronal line as growth
goes on (figs. 28-31, pp. 119-122).

1. Elderly male (not figured).—Both ascending and horizontal limbs
present, and both on the outer face of the hemisphere. The coronal suture
crosses the base of the ascending limb, whilst the horizontal limb skirts the
spheno-frontal suture.

2. Young male, twenty-five years old (fig. 12).—Both ascending and
horizontal limbs present on the outer surface of the hemisphere, but both
short. In the figure they are concealed by the bars of bone. The ascending
limb is placed along its whole length immediately behind the coronal
suture; the horizontal limb lies immediately above the fore-part of the
spheno-parietal and the back part of the spheno-frontal sutural line.

3. Elderly male, seventy-five years old (fig. 16).—In this head a
portion of the insula is exposed through the non-development of the pars
triangularis. The exposed part of the insula is placed immediately behind
the coronal suture—the lip of the orbital operculum very nearly coinciding
with the coronal line.