singular differences which they exhibit, skull collecting and skull
measuring has been a zealously pursued branch of Natural History, and
the results obtained have been arranged and classified by various
writers, among whom the late active and able Retzius must always be the
first named.

Human skulls have been found to differ from one another, not merely in
their absolute size and in the absolute capacity of the brain case, but
in the proportions which the diameters of the latter bear to one
another; in the relative size of the bones of the face (and more
particularly of the jaws and teeth) as compared with those of the
skull; in the degree to which the upper jaw (which is of course
followed by the lower) is thrown backwards and downwards under the
fore-part of the brain case, or forwards and upward in front of and
beyond it. They differ further in the relations of the transverse
diameter of the face, taken through the cheek bones, to the transverse
diameter of the skull; in the more rounded or more gable-like form of
the roof of the skull, and in the degree to which the hinder part of
the skull is flattened or projects beyond the ridge, into and below
which, the muscles of the neck are inserted.

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.* 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