MUSCLES OF THE THORAX. 381 



lique muscle. It arises, also, fleshy from the anterior two- 

 thirds of the clavicle. The clavicular and sternal portions of 

 the origin are separated by an interval, giving the appearance 

 of two muscles. 



The fibres converge, and terminate by a broad, thin tendon, 

 which is inserted into a roughness on the exterior edge of the 

 bicipital fossa of the os humeri, and into the fascia brachialis, 

 just at the internal edge of the deltoid muscle. At this inser- 

 tion it adheres to the tendon of the latissimus dorsi. The un- 

 der edge of the muscle, near its insertion, is folded inwards and 

 upwards, which gives the rounded thick margin to the fore 

 part of the axilla. That part of the broad tendon belonging to 

 the clavicular portion is inserted lower down than the sternal, 

 which produces a decussation of the fibres of the tendon. 



The pectoralis major draws the arm inwards and forwards; 

 and also depresses it when it is raised.* 



The Pectoralis Minor, 



Is brought into view by raising the last muscle. It is com- 

 paratively small, and somewhat triangular. Arising by thin 

 tendinous digitations from the upper edges of the third, fourth, 

 and fifth ribs, it soon becomes fleshy, and is inserted, by a short 

 flat tendon, into the inner facet of the coracoid process of the 

 scapula. Its use is to draw the scapula inwards and down- 

 wards.f 



* Varieties. Sometimes a single fasciculus arises from the eighth rib, which 

 ascends towards the os humeri, has a tendon in its centre, and finally joins with 

 the tendon of the pectoralis minor; sometimes this muscle attaches a small fas- 

 ciculus to the brachialis internus; sometimes there is a small square plane of 

 muscular fibres on its front surface, decussating the fibres at right angles ; 

 sometimes a fasciculus almost cylindrical proceeds from it towards the axilla, 

 and, being changed into a long tendon, is inserted into the internal tuberosity of 

 the os humeri. Supernumerary fasciculi are also found going from one rib to 

 another, or towards the sternum; sometimes its tendon detaches a fasciculus, 

 which, crossing the insertion of the muscle, covers the bicipital groove of the oa 

 humeri like a bridge, is blended with the tendon of the supra-spinatus, and in- 

 creases the thickness of the capsular ligament of the shoulder joint. In a mus- 

 cular male subject, black, it was entirely deficient, except the external clavicular 

 half. The pectoralis minor was wholly wanting in the same. Deer. 1837. 



t Varieties. Sometimes it sends a fleshy fasciculus to the tendinous origin 

 of the coraco-brachialis. Sometimes, below it, there is a third pectoral muscle, 



