MAMMARY GLANDS. 821 



numerous orifices, the apertures of the lactiferous ducts. Near the base of the 

 nipple, and upon the surface of the areola, are numerous sebaceous glands, 

 which become much enlarged during lactation, and present the appearance of 

 small tubercles beneath the skin. These glands secrete a peculiar fatty sub- 

 stance, which serves as a protection to the integument of the nipple in the act 

 of sucking. The nipple consists of numerous vessels, which form a kind of 

 erectile tissue, intermixed with plain muscular fibres. 



Structure. The mamma consists of gland tissue ; of fibrous tissue, connecting 

 its lobes ; and of fatty tissue in the intervals between the lobes. The mammary 

 gland, when freed from cellular tissue and fat, is of a pale reddish color, firm 

 in texture, circular in form, flattened from before backwards, thicker in the 

 centre than at the circumference, and presenting several inequalities on its sur- 

 face, especially in front. It consists of numerous lobes, and these are com- 

 posed of lobules, connected together by areolar tissue, bloodvessels, and ducts. 

 The smallest lobules consist of a cluster of rounded vesicles, which open into 

 the smallest branches of the lactiferous ducts; these ducts uniting, form larger 

 ducts, which terminate in a single canal, corresponding with one of the chief 

 subdivisions of the gland. The number of excretory ducts varies from fifteen 

 to twenty ; they are termed the tubuli lactiferi, t. galactophori. They converge 

 towards the areola, beneath which they form dilatations, or ampulla, which 

 oerve as reservoirs for the milk, and, at the base of the nipple, become con- 

 tracted, and pursue a straight course to its summit, perforating it by separate 

 orifices considerably narrower than the ducts themselves. The ducts are com- 

 posed of areolar tissue, with longitudinal and transverse elastic fibres, and 

 longitudinal muscular fibres; their mucous lining is continuous, at the point of 

 the nipple, with the integument; the epithelium is of the tessellated or scaly 

 variety. 



The fibrous tissue invests the entire surface of the breast, and sends down 

 septa between its lobes, connecting them together. 



The fatty tissue surrounds the surface of the gland, and occupies the intervals 

 between its lobes and lobules. It usually exists in considerable abundance, and 

 determines the form and size of the gland. There is no fat immediately be- 

 neath the areola and nipple. 



Vessels and Nerves. The arteries supplying the mammae are derived from the 

 thoracic branches of the axillary, the intercostals, and internal mammary. The 

 veins describe an anastomotic circle round the base of the nipple, called by 

 Haller the circulus venosus. From this, large branches transmit the blood to the 

 circumference of the gland, and end in the axillary and internal mammary veins. 

 The lymphatics run along the lower border of the Pectoralis Major to the axil- 

 lary glands. The nerves are derived from the anterior and lateral cutaneous 

 nerves of the thorax. 



