PART II. 



OSTEOLOGY OF THE RABBIT. 



For a practical study of the rabbit's skeleton, a thoroughly cleaned, 

 but otherwise rough, unmounted skeleton will be found most convenient. 

 The skull should be divided with a fine saw at a little to one side of the 

 median plane, or a second skull may be provided for this purpose (cf. 

 Fig. 33). The most useful specimens for reference are: (1) a well- 

 mounted skeleton of the adult animal, showing the natural relations of 

 the bones; and (2) a rough skeleton of a young animal of from one to 

 five weeks, showing the primary composition of cartilage bones. For 

 the special study of the skull (pp. 85-97) a disarticulated specimen may 

 be employed, but the majority of the features may be made out in 

 the intact or divided skulls. The general account of the skull as 

 given below will be found to cover most of the osteological points 

 noted in the dissection. 



DIVISIONS OF THE SKELETON. 



The skeleton is divisible into two main portions, namely, the axial 

 skeleton and the appendicular skeleton. The former comprises the 

 vertebral column, the ribs, the sternum, and the skeleton of the head; 

 the latter, the supports of the anterior and posterior limbs, and the 

 associated pectoral and pelvic girdles. 



THE VERTEBRAL COLUMN. 



The vertebral column (columna vertebralis) is formed of a linear 

 series of segments, the vertebrae. In accordance with its function as a 

 general support of the body, and also its relations with the nervous 

 system and the spinal musculature, the vertebrae, with minor exceptions, 

 are constructed on the same plan. Those of particular regions also 

 present certain features in common, so that it is possible to classify 

 them into cervical, thoracic, lumbar, sacral, and caudal groups. 



A typical vertebra — for the characters of which any one of the 

 thoracic or lumbar series may be taken (Fig. 27, D-F) — consists of a 

 basal portion, the vertebral body (corpus vertebrae), and of a dorsal, 

 vertebral arch (arcus vertebrae). The two portions enclose a large 

 aperture, the vertebral foramen (foramen vertebrale). The successive 

 foramina form an almost complete tube, the vertebral canal (canalis 

 vertebralis), for the accommodation of the spinal cord. 



The body of a vertebra is a cylindrical, or somewhat dorsoventrally 

 compressed, mass of bone, which bears at either end an articular surface 

 for attachment to the adjacent vertebra. The articular surfaces are 

 borne on thin plate-like epiphyses, the epiphysial lines being evident 

 even in older animals, especially in the lumbar region. The dorsal por- 

 es 



