832 



OSSEOUS SYSTEM. (CoMp. ANAT.) 



The palatine bones (22) are easily recog- 

 nisable in Fishes, occupying the same place as 

 in Serpents (fig. 439), and, moreover, further 

 distinguished by being frequently armed with 

 teeth which project into the roof of the mouth. 

 In Reptiles, also, teeth are often attached to 

 them where they assist in forming the cavity of 

 the mouth. These bones are found in all the 

 vertebrate classes. 



The transverse bones (24) occupy nearly the 

 same situation in Fishes as in Reptiles, but in 

 the latter they are most distinctly seen. In the 

 Crocodile each is a bone of considerable size, 

 composed of three branches and extending 

 between the pterygoid bone and the junction of 

 the jugal, the maxillary, and the posterior 

 frontal. This bone is not met with, either in 

 Birds or Mammalia, not even in the foetal 

 period of their existence. 



The internal pteryiioid bones(25) are like- 

 wise distinct in fishes, stretching between the 



Fig. 443. 



Fig. 444. 



Skull of a young Ostrich ( Strut hio Camelus). 



palatine bone and that which supports the 

 lower jaw (26). In Reptiles they are large and 

 important detached bones, occupying the po- 

 sition of the pterygoid processes of the sphe- 

 noid ; but in Birds and Mammals they become 

 completely anchylosed with the sphenoid, so 

 that, by the human osteologist, they are erro- 

 neously regarded as apophyses of that bone. 



Section of skull of young Ottrich. 



The zygomatic, Owen, (jiigal, Cuvier,) are 

 in Fishes broad pieces, generally of a triangular 

 shape, placed behind the transverse, which by 

 their inferior angle support the articulation 

 of the lower jaw. In Reptiles, too, it may al- 

 ways be distinguished by the latter circum- 

 stance, and in Serpents it is particularly re- 

 markable (Jigs. 438, 439, 26), standing out 

 from the squamo-temporal (mastoid, Cuv.) 

 like a branch, and thus giving that extraor- 

 dinary mobility to the articulation of the in- 

 ferior maxilla which enables those Reptiles to 

 swallow prey so disproportioned to the size of 

 their mouths. In other Reptiles this mobility 

 is in a great degree lost. But in Birds the 

 zygomatic bones again assume very important 

 functions. They are here known by the name 

 ossa quudrata, and standing out to a con- 

 siderable distance from the skull allow of great 

 mobility to the zygomato-maxillary articulation, 

 and also to the bones supporting the superior 

 maxilla. In Mammalia this zygomatic bone 

 is so firmly and undistinguishably united to 

 the temporal that the human osteologist merely 

 calls it the zygomatic process of that bone. 



The ma&to-temporal, Owen, (temporal, Cuv 

 23), are in Fishes and Reptiles distinct elements 

 of the skull, which in the human cranium are 

 consolidated with the other elements com- 

 posing the " os tewporis." 



