Man 70°-80° Cat 41° Dog 28°-41° Sheep 20°-25° Ox 18°-20° Ass 12°-16° Horse 11°-13°
Besides, in animals the cranium is very prominent superiorly, and the face, more or less elongated, is sharply projected downwards and forwards; in man the cranial region occupies not only the superior, but also the posterior part; the face is short and of a compact form. The human head, in its general aspect, may be compared to a sphere, while the skull of the quadrupeds presents the aspect of a quadrangular pyramid, with the base turned upwards and the summit at the incisor teeth.
=Direction of the Head.=--Before entering on the study of the bones of the head, it is necessary, in our opinion, to agree as to the position in which we shall suppose it to be placed.
The question may seem to be one of little importance; nevertheless, it cannot be regarded as indifferent, since authors are not all agreed on this subject.
Some suppose it to be placed vertically--that is, with the incisor teeth turned directly downwards. Others, on the contrary, suppose it to be placed horizontally, resting on the whole length of the lower jaw, the face being then turned upwards. These two extreme methods of arrangement appear to us to possess inconveniences--at least, for comparison with the human head.
[Illustration: FIG. 56.--HUMAN SKULL: MEASURE OF THE FACIAL ANGLE BY THE METHOD OF CAMPER. ANGLE BAC = 80°.
The internal wall of the cranial cavity is marked by the dotted line.]
[Illustration: FIG. 57.--SKULL OF THE HORSE: MEASURE OF THE FACIAL ANGLE BY THE METHOD OF CAMPER.[18] ANGLE BAC = 13°.
The internal wall of the cranial cavity is shown by the dotted line.]
[18] We have indicated on this sketch of the skull of the horse the facial angle measured by the method of Camper, in order that the correspondence with Fig. 56 may be more complete. But it is certain that the procedure here employed is in practice not satisfactory, since the apex of the angle, as we can demonstrate, is found to be situated within the contour of the head, and that, consequently, it is rather difficult to localize it precisely in the case of a given skeleton. Further, because of the absence of the base of the nose in the complete skull, the auriculo-nasal line cannot be accurately fixed. It would be the same for most other animals. This is why the method employed for these latter is preferably that of Cuvier, or, again, that of Cloquet. In the former, the apex of the angle of Camper is transferred to the free border of the upper incisors, but these teeth may be absent, and, on the other hand, ruminants are destitute of them. In the second, the same apex is placed at the alveolar border, and the angle then becomes fairly easy to appreciate.