100 



Anatomy of the Racbtt. 



tmi 



THE CLAVICLE. 



The clavicle (clavicula) is imperfectly developed in the rabbit, con- 

 sisting of a slender, arcuate rod of bone, tipped by cartilage, which lies 

 in the interspace between the manubrium sterni and the head of the 

 humerus. It occupies only a portion of this interspace, being attached 

 medially by the sternoclavicular ligament and laterally by the cleido- 

 humerai ligament. 



THE HUMERUS. 



The humerus (Fig. 38) is typical of the long bones of the proximal 

 and middle segments of the fore and hind limbs in consisting of a central 

 portion, the body or shaft of the bone, and 

 of proximal and distal extremities for muscle 

 attachment and articulation. The proxi- 

 mal extremity bears on its medial side a 

 smooth, convex projection, the head of the 

 humerus (caput humeri), for articulation 

 with the scapula. The articulation is 

 nominally a ball-and-socket joint, or enar- 

 throsis, but the articulating surfaces are 

 somewhat restricted, and the muscular 

 arrangements of the limb are such that the 

 range of lateral motion (abduction and 

 adduction) is small. Immediately in front 

 of the head of the bone there is a small 

 elevation, the lesser tubercle (tuberculum 

 minus). It is separated by a longitudinal 

 furrow of the anterior surface, the inter- 

 tubercular groove (sulcus intertubercularis), 

 from a much larger lateral elevation, the 

 greater tubercle (tuberculum majus). Ex- 

 tending distad from the latter is a tri- 

 angular area, the humeral spine (spina 

 humeri), the tip of which reaches almost 

 to the middle of the bone and forms a 

 pronounced angle on its anterior surface. 



The distal extremity of the humerus 

 bears a grooved articular surface, the 

 trochlea humeri, for articulation with the 

 radius and ulna. On its lateral side is a 

 smaller surface, the capitulum humeri, for 

 articulation with the radius alone. Im- 

 mediately above the trochlea the medial and 

 lateral portions of the bone are thickened to 

 form two areas for muscular attachment. 



One of these, the lateral epicondyle (epicondylus lateralis), is a general 

 point of origin for the extensor muscles of the dorsal surface of the 

 hand, while the other, the medial epicondyle (epicondylus medialis), is 



Fig. 38. Anterior surface of the left 

 humerus: c, capitulum; c.h., head of 

 humerus; e.l. and a.m., lateral and 

 medial epicondyles; f.r., radial fossa; 

 s.h., spina humeri; s.i., intertuber- 

 cular groove; t.h., trochlea humeri; 

 t.rai. and t.mj., lesser and greater 

 tubercles. 



