In some skulls the brain case may be said to be "_round_," the extreme length not exceeding the extreme breadth by a greater proportion than 100 to 80, while the difference may be much less.[49] Men possessing such skulls were termed by Retzius "_brachycephalic_," and the skull of a Calmuck, of which a front and side view (reduced outline copies of which are given in Figure 26) are depicted by Von Baer in his excellent "Crania selecta," affords a very admirable example of that kind of skull. Other skulls, such as that of a Negro copied in Fig. 27 from Mr. Busk's "Crania typica," have a very different, greatly elongated form, and may be termed "_oblong_." In this skull the extreme length is to the extreme breadth as 100 to not more than 67, and the transverse diameter of the human skull may fall below even this proportion. People having such skulls were called by Retzius "_dolichocephalic_." The most cursory glance at the side views of these two skulls will suffice to prove that they differ, in another respect, to a very striking extent. The profile of the face of the Calmuck is almost vertical, the facial bones being thrown downwards and under the fore part of the skull. The profile of the face of the Negro, on the other hand, is singularly inclined, the front part of the jaws projecting far forward beyond the level of the fore part of the skull. In the former case the skull is said to be "_orthognathous_" or straight-jawed; in the latter, it is called "_prognathous_," a term which has been rendered, with more force than elegance, by the Saxon equivalent,--"snouty." Various methods have been devised in order to express with some accuracy the degree of prognathism or orthognathism of any given skull; most of these methods being essentially modifications of that devised by Peter Camper, in order to attain what he called the "facial angle." [Illustration: FIG. 26.--Side and front views of the round and orthognathous skull of a Calmuck after Von Baer. One-third the natural size.] But a little consideration will show that any "facial angle" that has been devised, can be competent to express the structural modifications involved in prognathism and orthognathism, only in a rough and general sort of way. For the lines, the intersection of which forms the facial angle, are drawn through points of the skull, the position of each of which is modified by a number of circumstances, so that the angle obtained is a complex resultant of all these circumstances, and is not the expression of any one definite organic relation of the parts of the skull.