Chap, x.] THE THORAX. 153 



in the fourth or fifth space. It is most easily reached 

 through the second space, and cannot be secured 

 through any space below the fifth. 



The female breast extends from the third to 

 the fifth rib. It is supported by the superficial 

 pectoral fascia, which divides into two layers to 

 enclose it. The organ is made up of an accumulation 

 of racemose glands, which open into ducts discharging 

 at the nipple. In cases where during lactation the 

 acini are engorged with milk, the outlines of the 

 several, lobules and lobes of the breast are rendered 

 very distinct. The size of the breast depends usually 

 rather upon a deposit of fat collected about the organ 

 and distributed among its lobules than upon a 

 development of true gland tissue. A considerable 

 and rapid development of the mammary gland tissue 

 takes place at puberty, and the breast remains in its 

 most perfect anatomical condition during the child- 

 bearing period of life. After the cessation of men- 

 struation, the glandular tissue atrophies, although the 

 ducts always persist. The breast is thinner at the 

 periphery than at the centre, and is thinnest about a 

 line extending from the nipple to the sterno- clavicular 

 joint. Abscesses situated beneath the breast not un- 

 frequently make their way through the gland at some 

 point along this line. The base of the gland is flat, and 

 is separated from the pectoral muscle by much loose 

 connective tissue. It is in this tissue that the sub- 

 mammary abscess forms. There is sometimes a kind 

 of bursa between the breast and the muscle which has 

 been found to form a definite hygroma or bursal cyst 

 (Yelpeau). Although the gland is but loosely con- 

 nected with the pectoralis major, yet it moves a little 

 with that muscle, and the position of the breast can 

 be slightly affected by the movement of the arm. 

 It is important, therefore, that the arm should be 

 kept at rest in inflammatory affections of the organ. 



