114 THE OSTEOLOGY AND MYOLOGY 



described ; but the latter is more or less distinct. Fibres converge from their radiation 

 over the skin at large, to form a fan-shaped muscle, no longer adherent to the skin ; the 

 upper and lower borders of the muscle, after its separation from the skin, are in general 

 relation, respectively, with the posterior borders of the latissimus and great pectoral. The 

 muscle has definite insertion into the humerus along the outer border of the bicipital groove, 

 by a very thin, wide aponeurotic tendon, more or less blended, in different instances, with 

 the tendons of insertion of the pectorals. It retroducts the humerus, and appresses it to 

 the side of the body ; otherwise it is an adjuvant of the trunk muscles in curling up the 

 body, when it takes fixed point of action from the humerus. 



Om-o-anconeus {Dorso-qntrochllen Duv.). — (Fig. 28,?/.) Two or three inches from 

 the humerus the latissimus dorsi gives off from its under surfice, near its lower border, a 

 stout, flat, muscular slip, half an inch broad. This passes nearly at a right angle from the 

 latissimus, along the inner surface of the scapular head of the triceps, past the elbow, to be 

 inserted, by a definite tendon, into the ulnar olecranon, near the inner humeral condyle ; 

 and by a thin aponeurotic expansion blends with the general fascia of the forearm. Though 

 of comparatively small size, this muscle, from its very advantageous line of traction, is a pow- 

 erful adjuvant of the latissimus in retroducting the arm, and of the triceps in extending the 

 forearm. The design appears to be increase of power of curling the body, as, e. g., around 

 limbs of trees, etc. Although here appearing as actually only an offset from the latissimus, 

 it presents itself as really the homotype of the sartorius of the pelvic extremity. It is the 

 same as that described by Duvernoy in the Gorilla as " dorso-epitrochlien." There is no 

 attachment of this muscle by aponeurosis, or otherwise, to the scapula or thorax. 



The articulated parts of the scapular arch are joined together by a small muscle devoted 

 exclusively to this purpose, in addition to the usual joining by the indirect action of the 

 trapezius and deltoid. From the scapula five muscles act upon the humerus, and three 

 upon the forearm ; from the clavicle none proceed to the arm except part of the deltoid. 

 The muscles about the shoulder itself have much the same situation, shape and action as 

 in man ; but there is no teres minor. The coraco-brachialis is extremely small. There is 

 one (tricipital) extensor cubiti, and three flexors, the biceps being divided and inserted in 

 an interesting manner. 



Cleido-acromialis . — (Fig. 28, n.) A small muscle, distinct from the supraspinatus, and 

 almost, if not wholly, from the subclavius. It arises, by an aponeurotic tendon that becomes 

 fused with the fascia over the supraspinatus, from the acromion and proximal half of the 

 scapular spine ; runs transversely across the top of the shoulder, and along the correspond- 

 ing half of the clavicle, strengthening and protecting the loose, weak acromio-clavicular 

 articulation. Sometimes its under surface is somewhat blended with the termination of the 

 subclavius ; but it cannot be regarded as an extension of that muscle. I do not know what 

 name it may have already received. 



Subscapular is. — The want of convexity of the scapula causes this muscle to be thin and 

 flat. It arises from the periphery and greater part of the thoracic surface of the bone, and 

 is broadly inserted into the lesser tuberosity of the humerus, rotating the latter inward, and 

 thus directly antagonizing the infraspinatus. Its short, thick tendon passes across the 

 shoulder-joint, between the latter and the coraco-brachialis ; an aponeurosis radiates upon 

 the thoracic aspect of the muscle, much as in man ; many fleshy fibres take origin from this 

 fascial investment. 



