792 MAMMALIA. 



Man alone, after his infancy is past, walks thoroughly 

 erect. Though his head is weighted by a heavy brain, it 

 does not droop forwards. With his upright attitude the 

 increased command of vocal mechanism is perhaps in part 

 connected. Man plants the soles of his feet flat on the 

 ground ; the great toes are often longer, never shorter than 

 the others, and lie in a line with them; he has a better 

 heel than monkeys have. The arms are shorter than the 

 legs. There is no os centrale. There are 12 ribs and 17 

 dorso-lumbar vertebrae. 



Compared with the anthropoid apes, man has a bigger 

 forehead, a less protrusive face, smaller cheek-bones and 

 supra-orbital ridges, no sagittal or occipital crests, pro- 

 jecting nasals, an early disappearance of the suture 

 between premaxilla and maxilla, a true chin (hinted at in 

 the Gibbon), more uniform teeth forming an uninterrupted 

 horseshoe-shaped series without conspicuous canines. The 

 body is very naked ; the legs are relatively longer ; the 

 hallux is practically non-opposable ; there are no vocal 

 sacs ; there is at most a vestige of an os penis. 



More important, however, is the fact that the weight of 

 the gorilla's brain bears to that of the smallest brain of 

 an adult man the ratio of 2 : 3, and to the largest human 

 brain the ratio of i : 3 ; in other words, a man may have 

 a brain three times as heavy as that of a gorilla. The brain 

 of a healthy human adult never weighs less than 31 or 32 

 oz. ; the average human brain weighs 48 or 49 oz. ; 

 the heaviest gorilla brain does not exceed 20 oz. "The 

 cranial capacity is never less than- 55 cubic in. in any 

 normal human subject, while in the orang and chimpanzee 

 it is but 26 and 27^ cubic in. respectively." 



But, as Owen allowed long since, there is an "all-pervad- 

 ing similitude of structure " between man and the anthro- 

 poid apes. As far as structure is concerned, there is much 

 less difference between man and the gorilla than there is 

 between the gorilla and the marmoset. 



As regards the much-discussed question of a tail in man, it may be 

 noted that if we define a tail as that part of the body which contains 

 posts acrat vertebra and sundry other parts of primitive caudal segments , 

 and which is, moreover, completely surrounded by integument ', then such 

 tails occur always in early embryos of man, and as abnormalities after 



