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.
These facts are connected, moreover, with a group of observations and ideas which Gratiolet has brought forward on several occasions. According to this ingenious observer, the anterior sutures are the first to unite in inferior races, while in superior races the obliteration commences with the posterior sutures. Again, the sutures, as a whole, have a tendency to disappear rapidly in savage races, while the isolation of the bones of the cranium is persistent in civilized races, and particularly in the European White. This disposition allows a continuance of the development of the brain, although it gradually becomes slower. Gratiolet thus explains the continuance of the intellectual power, so remarkable in men who have constantly exercised their intelligence. The statistic researches of Dr. Pomerol, while correcting all that is absolute in this theory, seems to confirm it in some respects.
Since I am unable to review all the cranial characters, I shall pass by those drawn from the prominence of different bones, the occipital indices of Broca, the cephalo-spinal of Mantegazza, etc. I shall only say a few words upon the position of the foramen magnum, and the sphenoïdal angle of Welker, but I shall dwell more at length upon the capacity of the cranium.
D’Aubenton, in a special work, shows that the foramen magnum is always placed further back in animals than in man. Sœmmering remarked that it seemed more so in the Negro than in the White; and this opinion, which was apparently confirmed by some measurements, was at once accepted by a number of anthropologists, and regarded by them as a simian character, but this result was attained by considering the position of the aperture relatively to the entire length of the skull, including the face. Now it is at once evident that the forward development of the latter, by reason of prognathism, would increase the apparent retreat of the former.
The researches of M. Broca upon cranial projections enable us to state this problem correctly, and to give the solution of it. M. Broca compared 60 Europeans with 35 Negroes. Representing the total projection by 1000, he found that in the former the anterior projection was 475, and in the latter 498. The anterior border of the foramen magnum is then further removed from the alveolar border in the Negro than in the White, the difference being 23. But this projection includes, with the anterior cranial projection, the facial projection, which is 65 in the European and 138 in the Negro. If this is deducted from the former, we find that the White stands first in cranial projection alone, and that the difference is 50.
We learn from these calculations that, relatively to the cranium to which it belongs, the foramen magnum is placed more forward in the Negro than in the White, which is by no means the case in apes. These same calculations demonstrate the real difference which here distinguishes the two, that, namely, of the forward prolongation of the face.
In drawing comparisons between men and apes, the sphenoïdal angle discovered by M. Virchow, studied by M. Welker, and which, thanks to M. Broca, may be measured without making a section of the skull, presents special interest. It presents an inverse evolution in man, and the Quadrumana during growth. This may be seen from the annexed calculations borrowed from M. Welker:—
| MAN. | |
| 8 Infants | 141° |
| 10 Children from 10 to 15 years | 137° |
| 30 Adult Germans | 134° |
| —— | |
| Difference | -7° |
| APES. | |
| Sajou, at birth | 140° |
| ” adult | 174° |
| —— | |
| Difference | +34° |
| Orang., young | 155° |
| ” adult | 172° |
| ” old | 174° |
| —— | |
| Difference | +19° |
I have already insisted that facts of this nature are irreconcilable with those theories which attribute a more or less pithecoid ancestor to man.