414 PROFESSOR OWEN ON THE OSTEOLOGY OF 



21. The squamosal, lambdoidal, alisphenoidal and pterygoid air-cells. 



22. The more prominent cusps of the molar teeth. 



23. The larger relative size and more complex grinding surface of the last molar 

 tooth in both jaws. 



24. The larger relative size of the premolars, especially of the first. 



25. The more complex implantation of the premolars by three roots, two external 

 and one internal. 



26. The much larger and longer canines. 



27. The sexual distinction in the development of these teeth. 



28. The more sloping position of the crowns of the incisors. 



29. The broader and higher ascending ramus of the lower jaw. 



30. The total absence of the prominence of the symphysis forming the chin. 



In the form of the premaxillaries and the earlier obliteration of their sutures, the 

 smaller species of Chimpanzee more nearly resembles Man than the great Gorilla does ; 

 it seems also to deviate less through the minor development of the canine teeth, and of 

 the parietal and sagittal crests ; but it has been shown, in the comparison of the skulls 

 of the Troglodytes Gorilla and Troglodytes niger, § 3, that the latter departs in more 

 numerous and important particulars further from the Human type. 



^ 7. Concluding Observations. 



There finally remains for consideration the import and value of the differences which 

 have been pointed out between the great Chimpanzee — the most anthropoid of all known 

 brutes — and Man, in regard, more especially, to the often-mooted and lately-revived 

 hypothesis of the origination of the species of animals by gradual transmutation of 

 specific characters, and that in a progressive or ascending direction. 



It would be argued, in the spirit of that hypothesis, that the gradual cessation of 

 combative habits in successive generations of the Chimpanzee might be attended with 

 a diminution in the size of the canine teeth, and a concomitant subsidence of those 

 cranial cristae that are developed to increase the surface of attachment of the muscles 

 of the jaws ; whilst the cranial chamber might gradually expand under the influence of 

 circumstances inducing such peaceful habits, and tending to improve the instincts and 

 develope those psychical powers that dawn in the anthropoid apes, and the manifesta- 

 tions of which have been observed, always with interest and sometimes with astonish- 

 ment, in the young specimens of the Chimpanzees and Orangs that have been brought 

 alive to Europe. 



It is a well-established fact in human physiology, that the skeleton may be modified 

 to a certain extent by the action of the muscles to which it is subservient. By the 



