THE THEORY OF THE VERTEBRATE SKULL. 279 



only such a generalized statement of the facts of cranial structure 

 as this, but adds a hypothesis respecting the relations of the 

 skull to the spinal column. It assumes that the bony cranium (the 

 cartilaginous and membranous states of the cranium it usually, 

 ignores) is composed of elements homologous with those which 

 enter into the structure of the spiual column ; that, in fact, it 

 consists of modified vertebrae. And it is commonly conceived 

 that it is the doctrine of the unity of structure of the skull and 

 of the vertebral column, rather than the demonstration of the 

 unity of organization of skulls, which is one of the chief glories 

 of morphology. 



The assumption that every skull repeats the organization of 

 the trunk and consists of a certain number of modified vertebrae, 

 evidently implies a belief in the unity of organization of skulls ; 

 but it is to be carefully noted that the converse proposition does 

 not hold good ; for it is quite possible to hold that all skulls are 

 modifications of one fundamental plan, while wholly disbelieving 

 that plan to be similar to the plan of a vertebral column. 



Looking broadly at the history of the theory of the skull 

 (using the phrase in its widest sense), I note three great lines 

 of inquiry which have brought that theory into its present 

 condition,— -the first originated by Oken and Goethe ; the 

 second, not originated, perhaps, but chiefly fostered and deve- 

 loped by Geoffroy St. Hilaire and Cuvier ; the third, originated, 

 and almost exclusively worked out, by Keichert, Rathke, and 

 their followers among the embryologists of Germany and 

 England. 



I. I have united the names of Goethe and of Oken as the 

 originators of the hypothesis of the vertebral structure of the 

 skull, as a matter of equity, and to aid in redeeming a great 

 name from undeserved obloquy ; though, in strict technical 

 justice, the claim of the one to priority lapsed through lack of 

 publication. 



Goethe combined with a fervid creative genius, which has 

 placed him on a level with the greatest poets of all ages, so 

 much of observational acuteness and of intellectual precision 

 as might have sufficed for the equipment of a well-reputed 



