144 THE ASCENT OF MAN 



and face which cannot be carried further than in 

 Man. For the mode in which the cranial cavity is 

 gradually increased in size is a regular one, which 

 may be explained thus : we may look on the skull 

 as an irregular cylinder, and at the same time that 

 it is expanded by increase of height and width it 

 also undergoes a curvature or bending on itself, so 

 that the base is crumpled together while the roof 

 is elongated. This curving has gone on in Man 

 till the fore end of the cylinder, the part on which 

 the brain rests above the nose, is nearly parallel 

 to the aperture of communication of the skull 

 with the spinal canal, i.e. the cranium has a curve 

 of I So** or a few degrees more or less. This 

 curving of the base of the skull involves change in 

 position of the face bones also, and could not go 

 on to a further extent without cutting off the nasal 

 cavity from the throat. , . Thus there is 



anatomical evidence that the development of the 

 vertebrate form has reached its limit by com- 

 pletion in Man."^ 



This author's conception of the whole field of 

 living nature is so suggestive that we may continue 

 the quotation : " To me the animal kingdom appears 

 not in indefinite growth like a tree, but a temple 



iProf. J. Cleland, M.D., F.R,S., Jowml of Anatomy, Vol, 

 ;cviii., pp. 360-1. 



