268 ESSENTIALS OF ZOOLOGY 



with the muscles. The spine culminates in the rabbit in the 

 acromion and metacromion processes, and in other mammals 

 the former at least is usually evident. With it in the perfect 

 condition the clavicle is articulated. The narrow lower 

 extremity of the scapula is occupied by the glenoid cavity, and 

 it is also produced in front into the coracoid process. In the 

 young condition this is a separate cartilage and for a time a 

 separate bone. 



The clavicle is a membrane bone, but it is also associated 

 with cartilage, and is thus believed to be a product of the 

 membranous clavicle and the cartilaginous precoracoid. It 

 connects the scapula with the sternum. 



The humerus is a long bone and is divided into a shaft and 

 two extremities. The shaft is rounded or columnar in shape, 

 and presents in front a deltoid crest. The upper extremity 

 is rounded and capped with cartilage to enter into the formation 

 of the shoulder-joint with the scapula. Outside this articular 

 area there are the greater and lesser tuberosities separated by 

 the occipital groove. The lower extremity is expanded into 

 lateral condyles and a pulley -like surface divided into two by 

 a ridge. Above the articular surface in front is the coronoid 

 fossa and behind the olecranon fossa. The two may be so 

 deepened as to perforate the bone between them. The coronoid 

 fossa receives the coronoid process of the radius in flexion of 

 the lower limb, and the olecranon fossa the olecranon process 

 of the ulna in extension. 



The radius and ulna articulate with the humerus to form the 

 elbow -j oint . They are firmly attached, the radius being anterior 

 and medial in position, and the ulna posterior and external. 



The carpus consists of a series of small bones which allow 

 of the flexibility of the wrist. With the exception of the 

 sesamoid pisiform, they are cartilage bones. From the medial 

 to the lateral side they are as follows : 



Scaphoid (radiale), Semilunar (intermediale), Cuneiform (ulnare), 



Pisiform 



Centrale (usually absent in adult) 

 Trapezium Trapezoid Magnum Unciform 



I II III IV-V carpalia 



