416 PROFESSOR OWEN ON THE OSTEOLOGY OF 



the determination of the genera Troglodytes and Pithecus, have such an origin or depen- 

 dent relation. The great Chimpanzee, indeed, differs specifically from both the Orang 

 and Man in one cranial character, which no difference of diet, habit or muscular exer- 

 tion can be conceived to affect. 



The great prominent supraorbital ridge, for example, is not the consequence or con- 

 comitant of muscular development ; there are no muscles attached to it that could have 

 excited its growth. It is a characteristic of the cranium of the genus Troglodytes from 

 the time of birth to extreme old age : by the prominent supraorbital ridge, for example, 

 the skull of the young Chimpanzee with deciduous teeth may be distinguished at a 

 glance from the skull of an Orang at the same immature age ; the genus Pithecus, Geoffr., 

 being as well recognised by the absence, as the genus Troglodytes is by the presence of 

 this character. We have no grounds, from observation or experiment, to believe the 

 absence or the presence of a prominent supraorbital ridge to be a modifiable character, 

 or one to be gained or lost through the operations of external causes, inducing particular 

 habits through successive generations of a species. It may be concluded therefore that 

 such feeble indication of the supraorbital ridge, aided by the expansion of the frontal 

 sinuses, as exists in Man, is as much a specific peculiarity of the Human skull, in the 

 present comparison, as the exaggeration or suppression of this ridge is respectively 

 characteristic of the Chimpanzees and Orangs. 



The equable length of the human teeth, the concomitant absence of any diastema or 

 break in the series, and of any sexual difference in the development of particular teeth, 

 are to be viewed by the light of actual knowledge as being primitive and unalterable 

 specific peculiarities of Man. 



Teeth, at least the ordinary dentine of mammals, are not organized so as to be in- 

 fluenced in their growth by the action of neighbouring muscles ; pressure upon their 

 bony sockets may affect the direction of their growth after they are protruded, but not 

 the specific proportions and forms of the crowns of teeth of limited and determinate 

 growth. The crown of the great canine tooth of the male Troglodytes Gorilla began to 

 be calcified when its diet was precisely the same as in the female, when both sexes 

 derived their sustenance from the mother's milk. Its growth proceeded and was almost 

 completed before the sexual development had advanced so as to establish those differ- 

 ences of habits, of force, of muscular exercise, which afterwards characterize the two 

 sexes. The whole crown of the great canine is, in fact, calcified before it cuts the gum 

 or displaces its small deciduous predecessor : the weapon is prepared prior to the deve- 

 lopment of the forces by which it is to be wielded ; it is therefore a structure fore- 

 ordained, — a predetermined character of the Chimpanzee, — by which it is made physi- 

 cally superior to Man, and one can as little conceive its development to be a result of 

 external stimulus, or as being influenced by the muscular actions, as the development of 

 the stomach, the testes or the ovaria. 



The two external divergent fangs of the premolar teeth, and the slighter modifications 



