48 



ANATOMY OF THE RABBIT 



of compact tissue. If the bones of young animals are thoroughly 

 macerated, the epiphyses are usually found to be readily separable 

 from the main parts of the bones. 



In a comparison of the adult skeleton with the more primitive 

 embryonic skeleton, several differences in the arrangement of the 

 elements are evident. Thus many bones, nothwithstanding their 

 possession of several centres of ossification, are to be looked upon 

 as individual structures, while in other cases, as in the basal 

 portion of the skull, separate bone elements are produced in a mass 

 of cartilage primarily continuous. These either remain distinct 



K^^"^^ 



Fig. 26. Vertical sections of elbow and knee of four-day-old rabbit. 

 A, elbow: c, capsule; eb, endochondral bone in the distal epiphysis of the 

 humerus; ea, extensor muscles of the forearm; em, extensors of the hand; 

 fa, flexors of the forearm; fm, flexors of the hand; h, humerus; ol, olecranon; 

 r, radius; sc, synovial cavity; u, ulna. B, knee: a, anterior cruciate ligament; 

 c, capsule; f, femur; Ip, patellar ligament; p, posterior cruciate ligament; pv, 

 popliteal vessels; t, tibia; x,x, anterior and posterior ligaments of the lateral 

 meniscus; x'x', anterior and posterior ligaments of the medial meniscus. 



throughout life, or, as in the occipital region (Fig. 25), become fused 

 together to form compound or composite bones. In still other 

 cases, as in the vertebrae, the apparently single elements of the 

 adult condition are the products not only of originally distinct 

 bones, but also of primarily separate cartilage masses. 



The bones of the skeleton are united or articulated with one 

 another by connective tissue in the form of ligaments, by cartilage, 

 or in some cases by both together, i.e. by fibro-cartilage. The 



