76 



in comparison with other gibbons, but certainly is not so as respects 

 the higher Simiw. No details are given to illustrate the proposition 

 even in its more limited application; but the minor length of the 

 arms in the siamang, as compared with Hylobates lar, was probably 

 the obvious character in Vrolik's mind. 



The appearance of superior cerebral development in the siamang 

 and other long-armed apes is due to their small size and the con- 

 comitant feeble development of their jaws and teeth. The same 

 appearance makes the small platyrrhine monkeys of South America 

 equally anthropoid in their facial physiognomy, and much more 

 human-like than are the great orangs and chimpanzees. It is an 

 appearance which depends iipon the precocious growth of the brain, 

 as dependent on the law of its development. In all quadrumana 

 the brain has reached its full size before the second set of teeth is 

 acquired, almost before the first set is shed. If a young gorilla, 

 chimpanzee, or orang, be compared with a young siamang, of cor- 

 responding age, the absolutely larger size and better shape of brain, 

 the deeper and more numerous convolutions of the cerebrum, and 

 the more completely covered cerebellum., unequivocally demonstrate 

 the higher organization of the shorter-armed apes; 'in the structure 

 of the brain,' writes "Vrolik 1 , in accordance with all other com- 

 parative anatomists, 'they' (chimpanzee and orang-utan) ' approach 

 the nearest to man.' The degree to which the chimpanzee and 

 orang so resembled the human type seemed much closer to Cuvier, 

 who knew those great apes only in their immaturity, with their 

 small milk-teeth and precociously developed brain. Accordingly, the 

 anthropoid characters of the /Simia satyrus and Simla troglodytes, as 

 deduced from the facial angle and dentition, are proportionally 

 exaggerated in the Regne Animal 2 . As growth proceeds, the 

 milk-teeth are shed, the jaws expand, the great canines succeed 

 their diminutive representatives, the biting muscles gain a propor- 

 tional increase of carneous fibres, their bony fulcra respond to the 

 call for increased surface of attachment, and the sagittal and occipital 

 crests begin to rise : but the brain grows no more ; its cranial box 

 retains the size it shewed in immaturity ; it finally becomes masked 

 by the superinduced osseous developments in those apes which 

 attain the largest stature and wield the most formidably armed 

 jaws. Yet under this disguise of physical force, the brain is still 

 the better and the larger than is that of the little long-armed ape, 



1 Art. Quadnimana, Cyclopaedia of Anatomy, Vol. iv. p. 195. 



2 Ed. 1829, pp. 87, 89. 



