322 THE MUSCLES. 



radius by means of a synovial bursa, and is fixed within the ulna, towards the base of the 

 olecranon. 



The flexor hrachii or biceps of the Camel, is manifestly decomposable into two muaoular 

 portions, united above in a tendon. The inner portion is the largest and somewhat fusiform, and 

 is attached directly to the radius by its muscular fibres. The other portion, situated external 

 to and in front of the preceding, ends in a bifurcated tendon, one bratich of which goes to the 

 bicipital tuberosity ; the other, succeeded by a small fleshy fasciculis, joins the body of the 

 anterior extensor of the metacarpus. 



The short flexor of the forearm, or humeralis obliquus, is terminated in the Pig, Dog, and 

 Cat, by a small tendon which is fixed in the ulna, below the ulnar branch of tlie flexor 

 brachii. 



The middle extensor of the forearm and ancomus oi these animals are remarkable for their 



volume. 



Comparison of the Muscles op the Arm of Man with those of Animals. 



In Man, three muscles are situated in front of tlie humerus— the biceps, coraco-humeralis, 

 and the humeralis obliquus ; behind are found the triceps brachialis, and the anconeus. 



The biceps, which corresponds to the flexor brachii of animals, commences on the scapula 

 by two heads, which unite towards the upper part of the humerus. The long portion is 

 detached from the upper part of the rim of the glenoid cavity ; the shortest commences from 

 the summit of the coracoid process. Tlie inferior tendon of the biceps gives off", before fixing 

 itself on the bicipital tuberosity, a fibrous layer which is confounded with the antibrachial 

 aponeurosis. 



The coraco-humeralis has only one fleshy body. 



As in the Carnivora and Pig, the humeralis obliquus terminates on the ulna, below the 

 coronoid pi'ocess. 



The triceps brachialis exactly represents, by its three heads, the large, middle, and short 

 extensors of the forearm of animals (see Fig. 180). 



There is nothing particular with regard to the anconeus. 



Muscles of the Forearm. 



These muscles, nine in number, distributed in two regions — anterior and 

 posterior — envelop the bones of the forearm on every side except the internal, 

 where the radius is in mediate contact with the skin. They all terminate on 

 the different sections of the hand or anterior foot, which they flex or extend, 

 and are contained in a common fibrous sheath, which constitutes the antibrachial 

 aponeurosis. 



Antibrachial Aponeurosis. 



This retaining fascia forms a very strong and resisting envelope, which is 

 firmly fixed around the antibrachial muscles by the insertions it has on the bones 

 of the forearm, being attached to the olecranon, the internal aspect of the 

 radius, and to the inferior extremity of that bone, both inwards and outwards. 



Its external face is covered by the superficial vessels and nerves, which are 

 separated from the skin by a very thin fibrous layer, more particularly observable 

 on the inner side, where it covers the antibrachial aponeurosis in a very evident 

 manner ; it is rendered tense by the pectoralis transversus. Up to the present 

 time, this fibrous layer has not been distinguished from the aponeurosis it covers. 

 The inner face of the latter gives rise to several septa, which penetrate the 

 interstices of the muscles to form around some of them special retention sheaths ; 

 it adheres to several of them very intimately. At its upper border, this aponeu- 

 rosis receives, inwardly, the insertion of the annexed muscle of the latissimus 

 dorsi ; in front, the accessory band of the flexor brachii ; outwardly, it is con- 

 tinuous with the fascia covering the external face of the olecranian muscles. 

 Inferiorly, it is prolonged around the knee to form the tendinous sheaths of that 

 region. 



