266 ANATOMY OF THE RABBIT 



sertion: Distal portion of the upper third of the humerus 

 on its medial surface. 



4. Muscles arising from the scapula and humerus and inserted on 

 the proximal ends of the radius and ulna (extensors and flexors 

 of the forearm) (Figs. 37, 38, 102). 



A. Extensor (anconaeus) group. The muscles arise for the 

 most part behind the axis of the humerus, and are inserted on the 

 olecranon. 



(a) The extensor antibrachii parvus (anconaeus quartus). 

 Origin: Fascia of the medial surface of the humerus. In- 

 sertion: Medial surface of the olecranon. 



The muscle should be divided, or detached from its 

 origin, and reflected. 



(b) The anconaeus minimus (epitrochleonanconaeus). Origin: 

 Medial epicondyle of the humerus. Insertion: Medial 

 surface of the olecranon. 



(c) The triceps brachii. Origin in three portions. Caput 

 longum (anconaeus longus) : Ventral portion of the axillary 

 border of the scapula. Caput laterale (anconaeus lateralis) : 

 Greater tubercle and related portion of the lateral surface 

 of the humerus. Caput mediale (anconaeus medialis): 

 Posterior surface of the humerus. 



The three portions are almost separate muscles. Insertion 

 on the olecranon. 



B. Flexor group. The muscles arise in front of the axis of 

 the humerus and are inserted on the radius and ulna in front of 

 the elbow-joint. 



(a) The biceps brachii. Origin: Anterior border of glenoid 

 cavity. Insertion: Ventromedial surface of the ulna and 

 medial surface of the radius. The muscle possesses only 

 one head in the rabbit. 



(b) The brachialis. Origin: Anterior and lateral surfaces of 

 the humerus, divided unequally into a larger lateral and a 

 smaller medial portion by the insertion tendons of the 

 deltoideus and cleidohumeralis muscles. Insertion: In 

 common with the biceps. 



