Yet, generally speaking, it must be admitted, there is a great variation in prognathism among the Australians.
In order to compare the degree of facial prognathism of the skulls of different men, a method was devised by Fraipont: The glabella is connected with the lambda by an imaginary plane, and another plane erected at right angles to this at the glabella. The latter plane usually cuts the alveolar plane at about the first or second premolar, occasionally at the first molar. Still another plane is imagined, extending vertically from the most anterior point of the alveolar to the glabella-lambda plane. Then the rectangular distance between the two upright planes represents, after Fraipont’s method, the prognathism. The maximum prognathism of the Australian, determined by this means, is, according to Professor Klaatsch, twenty-five millimeters, and the minimum eight.
Let us now enquire into the possible origin of prognathism among the primitive races of mankind. We shall have to take note, in the first place, of the large occipital development of both the brain and the brain-box in the lower types of the human species. In order to antagonize the downward pull of this weight, the mandibular region has expanded and provides the balancing moment about a fulcrum on the spine. With this explanation fresh in our minds, we understand how the development of the frontal region of modern peoples would tend to modify the lower region of the face and establish the condition known as orthognathism.
Prognathism is usually associated with a receding chin. By elaborating the Fraipont method, Professor Klaatsch has added another vertical plane at the most anterior point of the cutting surface of the teeth. In primitive folks, like the Australians and the fossil Neanderthals, the chin lies behind this plane and is called a “negative chin”; in the Mongoloids (Malays, etc.) the chin practically lies against the plane and is called a “neutral chin”; and lastly, in the modern Europeans, the chin lies before the plane and is known as a “positive chin.”
In the Tasmanians, the chin was bluntly rounded, without much of the prominence so highly perfected in the modern peoples.
The mental foramen is usually situated at a point below and between the second bicuspid and first molar.
The Australian’s ear is large and longish, much the same in general appearance as the European’s; the Negroid’s ear is decidedly rounder. There is, however, no great racial variety in the human ear; man has, like the rodents, retained the primitive shape, whilst the monkeys have acquired more specialized forms.
The small process, known as the tragus, which partially covers the ear-hole, is mostly covered with bristly hairs in adult men.
The dependent portion, or lobulus, which carries the earrings of our European ladies and is often mutilated by the lower races, is not as a rule interfered with by the Australians. The custom of piercing the lobulus appears to be confined to the Cape York Peninsula in Queensland. The hole is pierced with a small pointed bone, after which a short cylindrical wooden rod or bone is inserted, frequently removed and replaced again, until the edge of the hole has healed. In the course of time, a series of rods, of gradually increasing diameter, are forced into the perforation, until a large pendant loop is formed. Upon special occasions, short painted rods of wood, two inches or more in diameter, are inserted into the loop.
The cheek bone, or zygomatic arch, is usually horizontal; but it may curve upwards from the squamous bone, thence downwards anteriorly. The mastoid process is comparatively small, but it is often associated with an unusual thickness of the wall of the ear-passage.