'f e', the basifacial axis; 'c b a', occipital angle; 'T i a',
tentorial angle; 'd a b', olfactory angle; 'e f b', cranio-facial angle;
'g h', extreme length of the cavity which lodges the cerebral
hemispheres or 'cerebral length.' The length of the basicranial axis
as to this length, or, in other words, the proportional length of the
line 'g h' to that of 'a b' taken as 100, in the three skulls, is as
follows:--Beaver 70 to 100; Lemur 119 to 100; Baboon 144 to 100. In an
adult male Gorilla the cerebral length is as 170 to the basicranial
axis taken as 100, in the Negro (Fig. 29) as 236 to 100. In the
Constantinople skull (Fig. 29) as 266 to 100. The cranial difference
between the highest Ape's skull and the lowest Man's is therefore very
strikingly brought out by these measurements. In the diagram of the
Baboon's skull the dotted lines 'd1 d2', etc., give the angles of the
Lemur's and Beaver's skull, as laid down upon the basicranial axis of
the Baboon. The line 'a b' has the same length in each diagram.

In such a mammal as a Beaver (Fig. 28), a line ('a b'.) drawn through
the bones, termed basioccipital, basisphenoid, and presphenoid, is very
long in proportion to the extreme length of the cavity which contains
the cerebral hemispheres ('g h'.). The plane of the occipital foramen
('b c'.) forms a slightly acute angle with this 'basicranial axis,'
while the plane of the tentorium ('i T'.) is inclined at rather more
than 90 degrees to the 'basicranial axis'; and so is the plane of the
perforated plate ('a d'.), by which the filaments of the olfactory nerve
leave the skull. Again, a line drawn through the axis of the face,
between the bones called ethmoid and vomer--the "basifacial axis" ('f
e'.) forms an exceedingly obtuse angle, where, when produced, it cuts
the 'basicranial axis.'

If the angle made by the line 'b c'. with 'a b'., be called the