.356 THE MECHANICAL FUNCTIONS. 



several elements are thrown into unusual positions, 

 and being variously distorted and disfigured, can 

 hardly be recognized under the strange disguises 

 they assume. 



The extensive researches that have been recently 

 made in this branch of comparative anatomy, have 

 supplied many facts which have been adduced by 

 the supporters of the hypothesis that the bony 

 coverings of the brain are the result of the deve- 

 lopement of three vertebrae. According to this 

 theory, the first of these supposed cranial vertehree, 

 beginning our enumeration from the neck, is the 

 origin of the occipital bone, of which the lower 

 part, or that which immediately supports the cere- 

 bellum, corresponds to the body of the vertebra ; 

 the two lateral portions, to the leaves ; and the 

 upper flat plate, to the spinous process. The body 

 of the second cranial vertebra becomes, in process 

 of time, the posterior half of the sphenoid bone, 

 which lies in the middle of the basis of the skull ; 

 the temporal bones being formed by its leaves, and 

 the parietal bones by the lateral halves of its spi- 

 nous process. The third cranial vertebra is con- 

 stituted by the anterior half of the sphenoid bone, 

 which is its body, and the frontal bones, which are 

 its leaves. This theory, which originated with 

 Dumeril,* was fondly nurtured by the poetic mind 

 of Goethe,t was extended by Oken, and adopted 

 by Spix, Meckel, Carus, and other German phy- 

 siologists. It has been farther applied to the bones 

 of the face, by GeofFroy St. Hilaire, who conceives 



* Considerations generales sur I'analogie entre tous les os et les 

 muscles du tronc des animaux. Magazin Encyclopedique. 1808. 

 f Zur Naturwissenschaft Uberhaupt, &c. 1817-24. 



