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 
theel than monkeys have. The arms are shorter than the 
legs. ‘[here is no os centrale. There are 12 ribs and 17 
-dorso-lumbar vertebree. 
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 
thallux 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 1 : 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 02z.;3: 
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 274 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 ¢hat part of the body which contains 
postsacral vertebra and sundry other parts of primitive caudal segments, 
and which ts, moreover, completely surrounded by integument, then such 
‘tails occur always in early embryos of man, and as abnormalities after 
