152 
The diagrams in figure 30 are reduced from very care- 
fully made diagrams of sections of four skulls, two round 
and orthognathous, two long and prognathous, taken longi- 
tudinally and vertically, through the middle. The sectional 
diagrams have then been superimposed, in such a manner, 
that the basal axes of the skulls coincide by their anterior 
ends, and in their direction. The deviations of the rest of 
the contours (which represent the interior of the skulls only) 
show the differences of the skulls from one another, when 
these axes are regarded as relatively fixed lines. 
The dark contours are those of an Australian and of a 
Negro skull: the light contours are those of a Tartar skull, 
in the Museum of the Royal College of Surgeons; and of a 
well developed round skull from a cemetery in Constanti- 
nople, of uncertain race, in my own possession. 
It appears, at once, from these views, that the prognathous 
skulls, so far as their jaws are concerned, do really differ 
from the orthognathous in much the same way as, though 
to a far less degree than, the skulls of the lower mammals 
differ from those of Man. Furthermore, the plane of the 
occipital foramen (4 c) forms a somewhat smaller angle with 
the axis in these particular prognathous skulls than in the 
orthognathous ; and the like may be slightly true of the 
perforated plate of the ethmoid—though this point is not so 
clear. But it is singular to remark that, in another respect, 
the prognathous skulls are less ape-like than the orthogna- 
thous, the cerebral cavity projecting decidedly more beyond 
the anterior end of the axis in the prognathous, than in the 
orthognathous, skulls. 
It will be observed that these diagrams reveal an im- 
mense range of variation in the capacity and relative pro- 
portion to the cranial axis, of the different regions of the 
cavity which contains the brain, in the different skulls. Nor 
is the difference in the extent to which the cerebral overlaps 
the cerebellar cavity less singular. A round skull (Fig. 30, 
Const.) may have a greater posterior cerebral projection than 
a long one (Fig. 30. Negro). 
