SKELETON OF THE BATRACHIA. 443 



pole are lost long before there is time for their 

 being ossified ; but those nearest to the body are 

 consolidated into one long and straight os coccy- 

 gis, which being joined to the sacrum at an angle, 

 gives rise to the strange deformity observable at 

 that part of the back of a frog ; for it here looks 

 as if it had been broken. The spinal cavity is 

 at the same time obliterated, that portion of 

 the spinal marrow which had passed through it 

 in the aquatic life of the animal being now with- 

 drawn. 



The theory of the spinal origin of the cranial 

 bones receives considerable support from their 

 structure and relative position in the skeleton 

 of the frog. The cavity for the lodgement of 

 the brain, which is enclosed by these vertebrae, 

 is perfectly continuous in the same line with 

 the spinal canal, which, indeed, it scarcely 

 exceeds in its diameter. The bones of the face 

 are, at the same time, expanded laterally, so 

 as to bear no proportion to the cranial cavity. 

 The head plays on the vertebral column by two 

 lateral articular surfaces, formed upon the root 

 of each leaf of the occipital bone, while its body, 

 or basilar portion, is scarcely connected with 

 the first cervical vertebra, and has no articular 

 surface. 



In place of ribs, we find only small slender 

 detached bones, or rather cartilages, affixed to the 

 extremities of the transverse processes of some 



