254 THE MUSCLES. 



3. Coraco-humeralis, Coraco-brachialis, or Omo-lrachialis. (Fig. 121, 10.) 

 {Synonyms. Coraco-humeralisPercivall. Middle scapulo-humeralisLeyh., 



Volume Situation Direction. A small elongated muscle, which ap- 

 pears to belong to the arm rather than the shoulder, as it is situated at the 

 internal face of the humerus, whose direction it slightly crosses. If it is 

 described as in the subscapular region, it is because of its attachments and 

 action, which are, in every respect, analogous to those of the other muscles 

 of the shoulder. 



Attachments Form Structure. It commences on the beak of the 

 coracoid process by a small flat tendon, which is at first included between the 

 supraspinatus and subscapularis, but afterwards leaves the interstice formed 

 by these two muscles, to glide and be inflected over the terminal tendon of the 

 latter. This small tendon is succeeded by two muscular branches, one deep, 

 the other superficial. The first is a wide, thin, and short band, almost 

 entirely muscular, attached to the body of the humerus above the internal 

 tuberosity. The second forms a fleshy body of a certain thickness, flattened 

 on both sides, and strongly aponeurotic; the fasciculi composing it are 

 longer as they are more posterior, and are inserted, by their inferior extre- 

 mities, into the imprints on the anterior face of the humerus. 



Relations. This muscle is covered by the coraco-radialis, and by the 

 sterno-trochineus, which is partly attached to its tendon. It covers the 

 internal insertion of the subscapularis, the humerus, the common tendon of 

 the great dorsal, and the adductor of the arm, and a small portion of the 

 short flexor and middle extensor of the fore-arm. Its posterior border is 

 margined by the vascular and nervous trunks on the inner aspect of the arm. 

 The anterior humeral nerve passes between its two branches, along with an 

 arterial and venous ramification. 



Action. It is an adductor of the arm, and makes it also pivot inwards. 

 Its direction and the disposition of its attachments do not permit it to 

 produce rotation outwards, though 'it has been stated to do so by several 

 authors. 



4. Small Scapulo-Jiumeralis, 



{Synonyms. Not mentioned by Percivall. Leyh, in addition to the above designation, 

 names it the tensor of the capsular ligament.) 



The scapulo-humeralis gracilis is a very small cylindrical fasciculus, 

 comprised between the large extensor of the fore-arm and the capsule of the 

 scapulo-humeral articulation ; deriving its origin above the margin of the 

 glenoid cavity of the scapula, and terminating below the head of the humerus 

 by a thin tendon, which insinuates itself between the fibres of the short 

 flexor of the fore-arm. This muscle appears to be peculiar to Solipeds, and 

 has been regarded by Bigot as intended to raise the capsule of the scapulo- 

 humeral articulation during flexion, so as to prevent its being pinched 

 between the articular surfaces. 



DIFFERENTIAL CHAEACTEBS OF THE MUSCLES OF THE SHOULDER IN OTHER THAN SOLIPED 



ANIMALS. 



The Carnivora are the only animals which offer somewhat notable differences in 

 the muscles of the shoulder. 



Thus, the long abductor of the arm, very developed, has an anterior portion arising 

 directly from the acromion, and a posterior portion which springs from the whole extent 



