THE VISCERA. 255 



the anterior surface of the Thorax (before the third to the sixth 

 ribs) covered with fat and a delicate smooth skin, in the centre of 

 which rises the conical teat, or nipple, papilla mamma, surrounded 

 by a rosy or brownish halo, areola. The bosom, sinus, is the 

 space between the two mammae. 



Structure. The gland, freed from fat, is flattish, round, and rests upon the 

 m. pectoral mo/., with its flat base, separated by fasc. superficialis. The sur- 

 face is irregular, because the gland chiefly consists of irregular lobules, which 

 are associated together by uniting and adipose tissue, but do not communicate 

 with one another. [They are placed in a fibrous tissse, a kind of proper 

 fascia, pointed out by Sir Astley Cooper, in his work on the Breast. THAJTS.] 

 The lobules again consist of roundish vesicles arranged together, like a bunch 

 of grapes (acini, cellula, vesicuke), the white excretory ducts of which unite 

 together to form a large milk duct, ductus lactiferi, of which twelve to twenty 

 finally remain passing inwards towards the central point of the gland, and 

 open in the nipple, between the wrinkles of the skin, either singly, or two or 

 three united together. 



The vesicles consist of fibrous tissue, which also unites the lobules and 

 gives to the gland its firmness. The milk ducts are surrounded by erectile 

 tissue both in the areola, where they form enlargements, and in the nipple 

 itself, in consequence of which the nipple in suckling, or from physical 

 causes, becomes erect. 



In the male breast the vesicles and ducts are wanting. 



Vessels: Branches of artt. mammaria externa, very strong during suckling] 

 Veins: circulus venosus areola ; they open into Vv. mammar. extern. Lympha- 

 tics : they enter the axillary glands and plex. mammarius. 



Nerves : Branches of nn. supraclaviculares from the fourth cervical nerve to the 

 skin; very delicate twigs probably enter the gland with the arteries. [Fila- 

 ments of nervi intercostalesJ] 



