250 CRANIA AMERICANA.
The zygomatic diameter is the distance, in a right line, between the most prominent points of the zygomae.
The facial angle* is ascertained by an instrument of ingenious construction
* The facial angle, which was first proposed by the learned Professor. Camper, is measured in the following manner : a line called the facial line, is drawn from the anterior edge of the upper jaw, (or, if the tooth projects beyond the jaw, from the tooth itself,) to the most prominent part of the forehead, which is usually the space between the superciliary ridges. A second or horizontal line, is drawn through the external opening of the ear (meatus auditorius) till it touches the base of the nostrils, between the terminal roots of the front incisor teeth, and from this point it is still prolonged until it meets with the facial line already described : hence the two lines may meet at, or very near, the nasal spine, or base of the nose ; but in other instances the decussation of the lines occurs at a point considerably anterior to the bone. It is obvious that an angle will be formed where these lines thus intersect each other, and this is the facial angle. For example, notice the annexed wood cut, (No. 1,) which represents the skull of the Cowalitsk already figured in this work, (see Plate 50.) The line A, B, is the facial line, extending, as just observed, from the anterior margin of the upper jaw to the most prominent part of the os frontis; the second or horizontal line, is represented between the points C and D, and for the purpose of having a fixed point for its anterior termination, I have uniformly carried it to the nasal spine, above and between the roots of the two front incisor teeth. The point E, where these lines decussate each other, is the facial angle, which in the present instance will be found to measure about sixty-six degrees.—The second wood cut (No.2) represents the lines as drawn on a much better formed head, that of a Peruvian Indian, in which the angle at E measures seventy-six degrees.
The most casual inspection of these diagrams will satisfy any one that the facial angle is no criterion of mental intelligence; and in justice to Camper we must add that he does not assert it to be so. In fact it chiefly gives the projection of the face in relation to the head, without conveying the least idea of the capacity of the cranium,
which is often the same in heads whose diameters are altogether different. The mere obliquity of the teeth contracts the angle; and what is yet more important, the space between the eyes from whence the facial line is drawn, may be very prominent, so as to give an angle of eighty degrees, while the forehead itself retreats so rapidly, that if the facial line were made to touch it, the resulting angle would not perhaps exceed sixty-five degrees.
"The maximum angle that can be embraced by the facial lines," says Camper, "is 100°: if we advance these lines still further, the head becomes preternaturally large, as in hydrocephalus. But it is surprising to observe that the most ancient Greek artists have chosen the very maximum of the facial angle, while the best Roman graveurs were satisfied with the angle of 95°.
"I have thus established the two extremes of obliquity in the facial line, viz: from 70° to 100'