278 



LECTURE XIV. 



ON THE STRUCTURE OF THE VERTEBRATE SKULL. 



THE THEORY OF THE VERTEBRATE SKULL. 



In the preceding Lectures I have, as far as possible, confined 

 myself to a statement of matters of fact, and to the conclusions 

 which immediately flow from the application of a very simple 

 method of interpretation to the facts. That method of interpre- 

 tation is based upon the principle that, in any two skulls, those 

 parts which are identical in their principal relations in the adult 

 state, and in the mode in which they reach this state (or in 

 their development) are corresponding, or homologous, parts, and 

 need to be denominated by the same terms. 



By the application of this method it has been possible to 

 demonstrate the existence of a fundamental unity of organiza- 

 tion in all vertebrate skulls ; and, furthermore, to prove that 

 all bony skulls, however much they may differ in appearance, 

 are organized upon a common plan, no important bone exist- 

 ing in the highest vertebrate skull which is not recognisable in 

 the lowest completely ossified cranium. 



The enunciation of these results alone is a " Theory of the 

 Skull," but it is by no means what is commonly understood as 

 the theory of the skull. 



For it will be observed that the statement just put forth 

 confines itself to a simple generalization of the observed facts 

 of cranial structure, and would be perfectly complete were the 

 skull a self-subsi stent structure, devoid of any connection with a 

 trunk. On the other hand, that doctrine to which the title of 

 " The Theory of the Skull " is ordinarily applied, embraces not 



