. Evidence as to man's place in nature . °, is as muchas 150° or 160° ; the cranio-facial angle may be 90° or less,and the vertical height of the skull may have a large propor-tion to its length. It will be obvious, from an inspection of the diagrams,that the basicranial axis is, in the ascending series of Mam-malia, a relatively fixed line, on which the bones of thesides and roof of the cranial cavity, and of the face, may besaid to revolve downwards and forwards or backwards, accord- 151 ing to their position. The arc described by any one bone orplane, however, is not by any means always in
. Evidence as to man's place in nature . °, is as muchas 150° or 160° ; the cranio-facial angle may be 90° or less,and the vertical height of the skull may have a large propor-tion to its length. It will be obvious, from an inspection of the diagrams,that the basicranial axis is, in the ascending series of Mam-malia, a relatively fixed line, on which the bones of thesides and roof of the cranial cavity, and of the face, may besaid to revolve downwards and forwards or backwards, accord- 151 ing to their position. The arc described by any one bone orplane, however, is not by any means always in proportion tothe arc described by another. Now comes the important question, can we discern, betweenthe lowest and the highest forms of the human craniumanything answering, in however slight a degree, to this revo-lution of the side and roof bones of the skull upon the basi-cranial axis observed upon so great a scale in the mammalianseries? Numerous observations lead me to believe that wemust answer this question in the Fig. 30.—Sections of ortliognathons (light contour) and prognathous (darkcontour) skulls, one-third of the natural size, o b, Basicranial axis ; h c, h c,plane of the occipital forameu ; d d, hinder end of the palatine bone ; e e, frontend of the upper jaw ; TT, insertion of the tentorium. 152 The diagrams in figure 30 are reduced from very care-fully made diagrams of sections of four skulls, two roundand orthognatlious, two long and prognathous, taken longi-tudinally and vertically, through the middle. The sectionaldiagrams have then been superimposed, in such a manner,that the basal axes of the skulls coincide by their anteriorends, and in their direction. The deviations of the rest ofthe contours (which represent the interior of the skulls only)show the differences of the skulls from one another, whenthese axes are regarded as relatively fixed lines. The dark contours are those of an Australian and of aNegro skull: the light contours are t
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