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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 143

given in Plates v., vi., vil, and viii. But my observations have not been
confined to the heads that are figured. Many others have been examined
with precisely the same result; and I may further state that it is not
necessary for this purpose to examine the brain in situ, although this is,
undoubtedly, the best and most accurate plan. A perfectly fresh brain
transferred at once from the cranium into a saturated solution of chloride
of zinc, if the removal has been carefully conducted, will, when hardened in
the usual way, show distinctly the infero-lateral border. If a series of
brains at different stages of growth prepared in this way be compared, the
infero-lateral border will be observed to hold the same relative position
in them all. We may fairly conclude therefore that it is fixed and
unalterable. At the same time Symington is perfectly correct in maintaining
that the Sylvian fissure, as growth advances, descends somewhat
on the surface of the cerebrum. He is only at fault in the theory which
he advances to account for this descent. To this aspect of the question
we shall return later on.

The growth-change in the position of the squamous suture is very
marked. At first the squamo-zygomatic bone is low, and does not override
the lower border of the parietal, but as growth advances it extends
more rapidly than the parietal bone, and ascends so as to overlap it to a
considerable extent. The sutural line is always regarded as coinciding with
the upper border of the squamous bone. The proportion of cranial vault
above and below the highest point of the suture line in the adult is 75 : 25,
whilst in the last month of foetal life it is 81*7 : 18'3.

The growth-changes which occur in the relations of the two bones at the
squamo-parietal suture are rendered clear in the four figures which are
given in pp. 119-122. The lower border of the parietal bone is brought out
on the exterior of each of the four skulls which are depicted by a series of
holes which have been drilled along the internal sutural line. A series of
measurements on these and other skulls established the following facts : 1.
That the lower border of the parietal bone virtually maintains the same
relative position throughout all periods of skull - growth ; and 2. That the
overlapping is entirely due to the upward growth of the squamosal bone.
Indeed we may take it as a law that the relations which the internal sutural