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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 21

callosum. It is no doubt true that the obliteration is very nearly synchronous
with this, but whether it is caused by it or not is altogether
another matter.

Sir William Turner, in the remarkable address which he delivered to the
anatomical section of the Tenth International Medical Congress in Berlin,
made a very significant and suggestive remark. He said: " The radiating
character of these fissures in the brains of Macropus and Halmaturus, in which
it must be remembered the corpus callosum is rudimentary, is of interest in
connexion with the radiated arrangement of the transitory fissures on the
cranial surface of the human brain at an early period of development."*
There would thus appear to be phylogenetic as well as ontogenetic evidence
in favour of the view that the development of the corpus callosum is in
some way connected with the disappearance of the transitory furrows.
Later on I shall endeavour to prove that, however this may be, there
are certainly other factors at work in bringing about this very curious
phenomenon.

Recently Dr. Alexander Bruce has published in the Proceedings of the
Royal Society of Edinburgh, vol. xv., a very able Paper upon a case of

Fig. 5.—Reproduction of Dr. Bruce's figure depicting a human brain in which the
corpus callosum was absent. P., upper end of a fissure supposed by Dr.
Bruce to be the fissure of Rolando ; PO., parieto-occipital fissure.

* " The Convolutions of the Brain : a Study in Comparative Anatomy," Journal of Anatomy
and Physiology, vol. xxv., p. 105.