40 MAMMALIA. 



cochlea, which terminates by one canal in the vestibule, and 

 by the other in the tympanum. 



Their cranium is subdivided into three portions; the ante- 

 rior is formed by the two frontal and ethmoidal bones, the 

 middle by the two ossa parietalia and the os ethmoides, and 

 the posterior by the os occipitis. Between the ossa parietalia, 

 the sphenoidalis and the os occipitis, are interposed the two 

 temporal bones, part of which belong properly to the face. 



In the foetus, the occipital bone is divided into four parts : 

 the sphenoidal into two halves, which are again subdivided 

 into three pairs of lateral wings ; the temporal into three, one 

 of which serves to complete the cranium, the second to close 

 the labyrinth of the ear, the third to form the parifetes of the 

 tympanum, &c. These bony portions, still more numerous in 

 the earliest period of the foetal existence, are united more or 

 less promptly, according to the species, and the bones them- 

 selves finally become consolidated in the adult. 



Their face consists of the two maxillary bones, between 

 which pass the nostrils ; the two intermaxillaries are situated 

 before, and the two ossa palati behind them ; between these 

 descends the vomer, a bony process of the os ethmoides ; at 

 the entrance of the nasal canal are placed the ossa nasi ; to its 

 external parietes adhere the inferior turbinated bones, the 

 superior ones which occupy its upper and posterior portion 

 belonging to the os ethmoides. The jugal or cheek bone 

 unites the maxillary to the temporal bone on each side, and 

 frequently to the os frontis ; finally, the os unguis, and pars 

 plana of the ethmoid bone occupy the internal angle of the 

 orbit, and sometimes a part of the cheek. In the embryo 

 state these bones also are much more subdivided. 



Their tongue is always fleshy, connected with a bone called 

 the hyoides, which is composed of several pieces, and sus- 

 pended from the cranium by ligaments. 



Their lungs, two in number, divided into lobes, and com- 

 posed of an infinitude of cells, are always enclosed, without 

 any adhesion, in a cavity formed by the ribs and diaphragm 

 and lined by the pleura; the organ of voice is always at the 



