MAMMALIA. 



663 



Mammifcrous skeleton are connected to each other are constructed 

 upon the same principles as in the human body, insomuch that to 

 describe them even in general terms would be useless. 



The bones of the cranium and face, as in Man, are joined toge- 

 ther by harmony or by suture. The articulations of the lower jaw 

 are double, each presenting an interarticular cartilage ; except in the 

 Cetacea, where, instead of such a structure, a very thick matted 

 ligamentous substance, having its interstices filled with oil, passes 

 directly from the condyles of the jaw to the temporal bones. 



The joints of the spine, thorax, and pelvis are all constructed 

 upon the same principles as the corresponding articulations in the 

 human subject ; and the same may, with slight exceptions, be said 

 of those of the extremities. The chief differences will be found in 

 the connection between the radius and ulna, the movements of 

 rotation becoming gradually less manifest as we descend from Man : 

 the tibia and fibula, too, ultimately become completely anchy- 

 losed to each other. The hip-joint contains an internal liga- 

 mentum teres ; but in a few instances, e. g. the Ornithorhyncus, the 

 Echidne, the Sloths, the Elephant, the Seals, and the Orang 

 Outang, this round ligament is deficient. The arrangement of the 

 other articulations will be at once apparent, on reference to the 

 figures of the different skeletons already given. 



(744.) Turning to the digestive system of Mammiferous ani- 

 mals, their 



teeth first in- Fi s- 310. 



vite our at- 

 tention. We 

 have already, 

 when describ- 

 ing the os- 

 seous frame- 

 work of these 

 elevated be- 

 ings, exposed 

 their general 

 arrangement 

 in the jaws 

 of the diffe- 

 rent orders ; 

 but it still 

 remains for us 



