MAMMARY GLAND. 227 



Structure. In its texture the mamma resembles those compound glands 

 which are formed by the vesicular endings of branched ducts. It consists 

 of small vesicles which are united to form lobules and lobes. Connected 

 with each lobe is an excretory or lactiferous duct. 



A layer of areolar tissue, containing fat, surrounds the gland, and 

 penetrates into the interior, subdiving it into lobes ; but in the ultimate 

 structure of the gland, and in the nipple and areola, there is not any fatty 

 substance. Some fibrous septa fix the gland to the skin, and support it ; 

 these are the ligamenta suspensoria of Sir A. Cooper. 



Vesicles. The little vesicles or cells at the ends of the most minute 

 ducts are rounded in shape, and when filled with milk or mercury are just 

 visible to the naked eye, being about the size of a small pinhole in paper. 

 (Cooper.) Each is surrounded externally by a close vascular network. 



Lobules and lobes. A collection of the vesicles around their ducts form 

 the lobule or glandule, which varies in size from a pin's head to a small 

 tare. By the union of the lobules the lobes are produced, of which there 

 are about twenty altogether, and each is provided with a distinct duct. 



The duels issuing from the several lobes (about twenty) are named from 

 their office galactophorus ; they converge to the areola, where they swell 

 into oblong dilations or reservoirs (sacculi) of one-sixth to one-third of an 

 inch in width. Onwards from that spot the ducts become straight ; and, 

 surrounded by areolar tissue and vessels, are continued through the nipple, 

 nearly parallel to one another, and gradually narrowing in size, to open on 

 the summit by apertures varying from the size of a bristle to that of a 

 common pin. 



Like many other excretory ducts, the milk tubes consist of an external 

 or fibrous, and of an internal or mucous coat ; they and the vesicles are 

 sheathed by a columnar epithelium, which becomes flattened towards the 

 outer opening. 



Beneath the skin of the nipple and areola are branched lubricating 

 glands, which open on the tubercles before mentioned. 



Bloodvessels. The arteries are supplied by the axillary, internal mammary, and 

 intercostal, and enter both surfaces of the gland. The veins end principally in 

 the axillary and internal mammary trunks ; but others enter the intercostal veins. 



The nerves are supplied from the anterior and lateral cutaneous branches of -the 

 thorax, viz., from the third, fourth, and fifth intercostal nerves. 



The lymphatics of the inner side open into the anterior mediastinal glands ; but 

 on the outer side they reach the axillary glands. 



Dissection (fig. 69). With the limb in the same position to the trunk, 

 the student is first to remove the fascia and the fat from the surface of the 

 great pectoral muscle. In cleaning the muscle the scalpel should be car- 

 ried in the direction of the fibres, viz., from the arm to thorax ; and the 

 dissection may be begun at the lower border on the right side, and at the 

 upper border on the left side. 



The fascia and the fat are to be taken from the axilla, without injury 

 to the numerous vessels, nerves, and glands in the space. The dissection 

 will be best executed by cleaning first the large axillary vessels at the outer 

 part, where these are about to enter the arm : and then following their 

 branches which are directed to the chest, viz., the long thoracic under 

 cover of the anterior boundary, and the circumflex and subscapular vessels 

 and nerves along the posterior boundary. Some arterial twigs entering 

 the axillary glands should be traced out. 



In taking away the fascia and fat from the muscles in the posterior 



