Anatomy of the Rabbit. 



;ostal cartilages of the ribs, and a portion of the nasal septum; 

 t is also found uniting the basal bones of the skull. In the embryo, 

 lowever, it forms the entire skeleton, with the exception of a small 

 )ortion which, as described below, is formed of membrane bone, 

 n the course of development, except in the situations indicated, 

 he cartilage is replaced by bon,e. 



Bone is a compact, resistant, but yet 

 somewhat elastic tissue, possessing much 

 - greater strength than cartilage, and therefore 

 forming a more perfect skeletal support. As 

 indicated below, its appearance as a tissue 

 differs somewhat according to its mode of 

 formation. The more typical structure (intra- 

 membranous bone) is illustrated in the 

 accompanying figure (q) of a ground trans- 

 verse section of the dried shaft of the femur. 

 Its dry weight consfsts of about one-third 

 animal matter and two-thirds mineral matter, 

 the latter being chiefly calcium phosphate. 

 The bone materials are deposited in layers 

 or lamellae, which are comparable to highly 

 modified white fibres of fibrous connective 

 tissue. The lamellae enclose between them 

 greatly branched spaces, the lacunae, in 

 which in the natural condition the bone-cells 

 are accommodated. On account of certain 

 differences in development, the lamellae are 

 disposed in different ways. Some are dis- 

 posed concentrically around' longitudinal 

 spaces, the Haversian canals, forming in 

 this way the so-called Haversian systems. 

 The canals are occupied in the natural con- 

 dition by bloodvessels. Others of them, the interstitial lamellae, 

 are disposed in a somewhat parallel fashion between the Haversian 

 systems; while a third series, the circumferential lamellae, 

 are disposed in a parallel fashion with respect to the periphery or 

 the internal surface of the bone. In the natural condition the bone 

 is enclosed except on it > articular surfaces by a layer of connective 



..c.t. 



Fig. 10. Divided femur 

 of the rabbit; c.t., can- 

 cellous tissue; « e., distal 

 epiphysis; e.l., epiphysial 

 line; m.c, marrow-cavity; 

 9., shaft. 



