DISTINCTIVE CHARACTERISTICS OF MAN. 



they are evidently intended to counteract this disposition ; and we accord- 

 ingly find ourselves able to keep up the head for the whole day with so 

 slight and involuntary an effort that no fatigue is produced by it. More- 

 over, the plane of the foramen magnum and the surfaces of the condyles 

 have a nearly horizontal direction when the head is upright ; and thus the 

 weight of the skull is laid vertically upon the top of the vertebral column. 

 If these arrangements be compared with those which prevail in other Mam- 

 malia, it will be found that the foramen and condyles are placed in the lat- 

 ter much nearer the back of the head, and that their plane is more oblique. 

 Thus, whilst the foramen magnum is situated in Man just behind the centre 

 of the base of the skull, it is found in the Chimpanzee and Orang-outang 

 to occupy the middle of the posterior third (Fig. 3) ; and, as we descend 

 through the scale of Mammalia, we observe that it gradually approaches 

 the back of the skull, and at last comes nearly into the line of its longest 



FIG. 3. 



View of the base of the Skull of Man, compared with that of the Orang-outang. 



diameter, as we see in the Horse. Again, in all Mammalia except Man, 

 the plane of the condyles is oblique, so that, even if the head were equally 

 balanced upon them, the force of gravity would tend to carry it forwards 

 and downwards; in Man, the angle which they make with the horizon is 

 very small; in the Orang-outang, it is as much as 37; and in the Horse, 

 their plane is vertical, making the angle 90. If, therefore, the natural 

 posture of Man were horizontal, the plane of his condyles would be brought, 

 like that of the Horse, into the vertical position ; and the head, instead of 

 being nearly balanced on the summit of the vertebral column, would hang 

 at the end of the neck, so that its whole weight would have to be supported 

 by some external and constantly acting power. But for this, there is 

 neither in the skeleton, the ligamentous apparatus, nor the muscular sys- 

 tem of Man, any adequate provision ; so that in any other than the ver- 

 tical position, his head, which is relatively heavier than that of most Mam- 

 malia, would be supported with more difficulty and effort than it is in any 

 other animal. 



27. The position of the Face immediately beneath the brain, so that its 

 front is nearly in the- same plane as the forehead, is peculiarly characteristic 

 of Man; for in the skulls of the Chimpanzee and Orang, which approach 

 nearest to that of man, the cranial portions are rather posterior to, than 



