The study of the horizontal cephalic index might lead to many other remarks. I shall only recall the results obtained by M. Diétrici. It appears from his calculations that, the total population of the globe given at 1288 millions, there are 1026 millions of dolichocephali, and only 262 millions of brachycephali. But the Berlin savant places in the first category the Chinese, who are mesaticephali, and must alone be reckoned at 421 millions. All these facts considered, it appears to me, from the tables of MM. Pruner Bey and Broca, and other data, received up to the present time, that the mesaticephali are much more numerous than either the brachycephali or dolichocephali. If mesaticephaly is taken in the sense pointed out above, the latter in their turn predominate over the brachycephali, owing chiefly to African black populations, which we are daily learning to estimate as much more dense than they were formerly thought to be. Retzius only compared the antero-posterior and transverse maximum diameters. Later investigators have sought the relation between the latter and the height of the cranium. The _vertical cephalic index_ has thus been obtained, the importance of which is at once evident. It plays an equally important part in the table of M. Pruner Bey, and gives rise to considerations analogous to those just discussed. I cannot, however, enter into all these details without exceeding the limits of this book. From the same motive I shall not mention the other measurements of the cranium, maximum and minimum _frontal diameters_, _total circumference_, _antero-posterior arc_, and others. The composition of the cranium can only vary within very narrow limits. Nevertheless, in Negroes, in ancient Egyptians, etc., the squamous portion of the temporal bone is sometimes united to the frontal without the partial interposition of the wings of the sphenoid. This is a remarkable fact, being in direct contradiction to the _principles of connections_, so justly regarded by Etienne Geoffroy as one of the most essential principles of comparative anatomy. In the preceding case, the composition of the cranium is altered by the suppression of a normal suture. This may also be caused by the appearance of an abnormal suture, by which two distinct bones are formed from a single one. Such is the case when the occipital bone seems to divide, so as to leave its upper portion free. We then have what has been called the _epactal bone_, or _bone of the Incas_, because Rivers and Tschudy imagined this conformation to be a character peculiar to the race. M. Jacquart, however, showed that it was merely the result of a cessation in the evolution of the occipital bone, of which examples are found in the most different human races. It is to a similar phenomenon that the persistence of the medio-frontal suture is due. This, again, is doubtless universal, but much more frequent in the Aryan white race than in coloured races, and especially in the Negroes.