SKELETON OF THE RABBIT. 549 



anterior process or clitoris — the homologue of the penis. 

 Beside the penis in the male lie the scrotal sacs, into which 

 the testes descend when the rabbit becomes sexually mature. 

 Along the ventral surface of the thorax and abdomen in the 

 female there are four or five pairs of small teats or mammae. 



The limbs have clawed digits, five on the fore-feet, four on 

 the hind-feet, and they are very hairy. 



Skin and Muscles. — The skin is thickly covered with hair, 

 and has the usual sebaceous and sudorific glands, besides 

 special glands, such as the perineal glands beside the anus, 

 the glands of the eyelids, the lachrymal glands, and the 

 mammary glands developed in the females. Between the 

 skin and the subjacent muscles there is a layer of fatty 

 tissue, known as the panniculus adiposus ; it is present in 

 all Mammals except the common hare, and forms the im- 

 portant blubber of whales and seals. Beneath the skin 

 there is a thin sheet of muscle called the panniculus 

 carnosus, and when this is removed with the skin, many 

 of the niuscles of head and neck, limbs and trunk are 

 disclosed. ' The student who wishes to study these, and to 

 compare them with their homologues in man, will find 

 minute practical directions in Parker's Zootomy. 



The Skeleton. — The bones, like those of other Vertebrates, 

 are developed either as replacements of pre-existent carti- 

 lages, or independent of any such preformations, but in all 

 cases through the agency of active periosteal membranes. 

 By themselves, however, must be ranked little sesamoid 

 bones, which are developed within tendons and near joints, 

 notably for instance, the patella or knee-pan. There is no 

 bony exoskeleton in any mammals except the armadillos, 

 unless we rank the teeth, which develop in connection with 

 the skin of the jaws, as in a sense exoskeletal. The verte- 

 bral centra of Mammals, except in Monotremes and Sire- 

 nians, have distinct terminal ossifications, known as epi- 

 physes, and the same distinctness of ossification is seen in 

 many of the larger bones. 



The vertebrae may be grouped as cervical (seven in 

 number), thoracic (with ribs), lumbar (without ribs), sacral 

 (fused to support the pelvis), and caudal. The faces of the 

 centra are more or less flat, and between adjacent vertebrae 

 there are inter-vertebral discs of fibro -cartilage. 



