600 MUSCLES OP THE CHEST. 



being filled by aponeurosis. The internal arise from the 

 sternum and inferior margin of each cartilage and rib, 

 descend backward, decussating the external, and are in- 

 serted into the superior margin of the cartilage and rib 

 below, as far back as the angles of the ribs. These two 

 sets are separated by the intercostal vessels and nerves. 



Function. To raise the ribs, and enlarge the chest in 

 inspiration, the first rib being first fixed by the scaleni. 



The subclavius arises tendinous from the cartilage of the 

 first rib, forms a small round muscle, situated immediately 

 beneath the clavicle, and is inserted into the exterior 

 half of this bone, as far back as the ligament connecting 

 the coracoid process and clavicle. 



Function. To draw the clavicle and shoulder down- 

 ward. 



The triangularis sterni arises from the posterior surface 

 and edge of the ensiform cartilage and lower part of the 

 sternum. Its fibres run obliquely outward and upward, 

 to be inserted by fleshy and tendinous digitations into the 

 cartilages of the third, fourth, fifth, and sixth, and some- 

 times as high as the second rib. 



Function. To draw the ribs down and aid in expiration. 



Situated upon the anterior lateral regions of the chest 

 are the two mammce or breasts. These are glandular or- 

 gans, and belong to the conglomerate order. They rest 

 upon the great pectoral muscles, and between the third 

 and seventh ribs. The skin over the breast is thin, smooth, 

 and soft, and in the virgin, of a rather pale, inclined to a 

 bluish tint. In those who have borne children, and are ad- 

 vanced in life, the skin loses its smoothness and becomes 

 wrinkled, more uneven, and of a darker color. About the 

 centre of the gland the nipple is seen, which may be either 

 long or short, sometimes so short that with difficulty the 

 child takes hold of it. It consists of the lactiferous or milk 

 ducts connected by cellular tissue. It presents the form of 

 a cone in the virgin, while it has a flattened, cribriform 

 appearance in one giving suck. It is capable of erection, 

 and is thought by some to have the erectile tissue, while 



