In anthropology, as in all science requiring observation, it is the averages which ought to be admitted as evidence; they alone have an absolute value, and can alone lead to positive results. Every isolated phenomenon has its individual value as regards its simple truth, but we are exposed to the greatest errors when we begin to generalise from it. The osseous system has been most studied.[111] In the osseous system, the head, and particularly the skull. We shall be obliged, later on, to refer to the value of cranioscopic proceedings, and the classifications resting on this base. The face, as well as the skull, has been the object of attentive inquiry; the smallest differences have been noticed, and almost all have been formed by some one or other into distinct characteristics. We may quote here Bérard’s classification, as resumed and developed by Isidore Geoffroy Saint-Hilaire. He divided the genus _homo_ into four groups:-- 1. The _orthognathi_, or men with a flat face and oval countenance. 2. The _eurygnathi_, or men with a large face and projecting cheek bones. 3. The _prognathi_, or men with a protuberant countenance. 4. Lastly, these races, which are both _eurygnathi_ and _prognathi_, like the Hottentots, the development of whose face offers an example of a manifest step towards the exaggeration of this same development in the anthropomorphous ape in infancy.[112] It has been endeavoured to establish, by means of averages, an appreciable difference between the pelvis of various races. Weber has considered that the form of the superior division is not the same with all of them. According to him it would be-- 1. _Oval_, among Europeans. 2. _Round_, among Americans. 3. _Square_, among the Mongols. 4. _Cuneiform_ or _oblong_, among the Africans. The same ideas have been resumed and defended by French anthropologists;[113] it is right, however, to remark, that Weber himself adds that varieties of every description of pelvis may be met with among the same race. That which appears certain is the fact, that in the Negro race the pelvis is, in general, sensibly smaller. This is, at least, the opinion of Camper,[114] Vrolik, Sömmering, White,[115] and Bérard,[116] who have measured a great number of them.