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modifications of that devised by Peter Camper, in order to 
attain what he called the ‘facial angle.’ 
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 orthog- 
nathism, 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 circum- 
stances, and is not the expression of any one definite organic 
relation of the parts of the skull. 
I have arrived at the conviction that no comparison of 
crania is worth very much, that is not founded upon the estab- 
lishment of a relatively fixed base line, to which the measure- 
ments, in all cases, must be referred. Nor do I think it isa 
very difficult matter to decide what that base line should be. 
The parts of the skull, like those of the rest of the animal 
framework, are developed in succession : the base of the skull is 
formed before its sides and roof ; it is converted into cartilage 
earlier and more completely than the sides and roof: and the 
cartilaginous base ossifies, and becomes soldered into one piece 
long before the roof. I conceive then that the base of the skull 
may be demonstrated developmentally to be its relatively fixed 
part, the roof and sides being relatively moveable. 
The same truth is exemplified by the study of the modifi- 
cations which the skull undergoes in ascending from the 
lower animals up to man. 
In such a mammal asa Beaver (Fig. 29), a line (a. 6.) 
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 (4. c.) forms a 
slightly acute angle with this ‘basicranial axis,’ while the 
plane of the tentorium (7. 7.) is inclined at rather more than 
90° to the ‘ basicranial axis’ ; and so is the plane of the perfo- 
