XVI THE MAMMALS OP INDIA. 



The bones of Mammals are distinguished from those of Birds by 

 the absence of air-cells, except in some of the cranial bones, and 

 these do not communicate with the lungs. Most of them are solid, 

 or, if hollow, are filled with a fatty or oily matter, termed marrow. 



The cervical vertebra? are always seven in number, without excep- 

 tion ; for in the Sloths, generally considered to have nine, it has been 

 lately demonstrated by Bell that the two posterior vertebrre (called 

 cervical) have rudiments of ribs attached to them, and are therefore 

 in reality modified dorsal vertebrae. The occipital bone articulates 

 with the atlas, or first vertebra, by two lateral condyles. 



The head is made up of numerous bones, which are divided into 

 the cranial, or those inclosing the brain, and the facial. The normal 

 number of facial bones is seventeen, viz., 2 nasal bones, 2 upper 

 maxillary, 2 intermaxillary, 2 lachrymal bones, 2 inferior turbinated 

 bones, 2 palatal bones, 2 jugal or malar bones, 2 lower-jaw bones, 

 and 1 vomer. Of these the nasal, upper and intermaxillary, and the 

 palatal bones bound the nasal cavity, and constitute the bony palate. 

 The cranial bones are eleven in number, viz., 2 frontal, 2 parietal, 

 2 squamous, and 2 tympano-petrous bones (which together make up 

 the two temporal bones), 1 occipital, 1 sphenoid, and 1 ethmoid. 



The orbit is bounded anteriorly by the molar and lachrymal 

 bones, and its posterior boundary is generally absent. The orbital 

 cavity is formed by processes from the frontal bones ; the lachrymal, 

 the molar, and sphenoid bones ; the ethmoid and palatine bones 

 occasionally assisting. The ethmoid, the turbinated bones, and the 

 vomer are internal, connecting the nasal bones with the base of 

 the skull. 



The lower maxillary bones, united at the chin, are movably 

 articulated with the temporal bone by a convex condyle, in this 

 differing from Birds and Reptiles, in which the articulation takes 

 place through a separate piece, the tympanic bone. In Man and 

 many Mammals several of these bones are united ; viz., the frontals, 

 the parietals in some Mammals, and the temporal bones. 



The number of dorsal vertebras depends on that of the ribs, and 

 varies from eleven to twenty ; and the lumbar, sacral, and coccygeal 

 vertebrae also vary from four to forty-five. 



