THE MAJ^^fARY GLANDS. 1179 



The nipple is a cylindrical or conical eminence capable of undergoing a sort of 

 erection from mechanical excitement, a change mainly due to the contraction of its 

 muscular fibres. It is of a pink or brownish hue, its surface wrinkled and provided 

 with papillae, and it is perforated at the tip by numerous orifices, the apertures of 

 the lactiferous ducts. Near the base of the nipple and upon the surface of the 

 areoli are numerous sebaceous glands, which become much enlarged during lacta- 

 tion, and present the appearance of small tubercles beneath the skin. These 

 glands secrete a peculiar fatty substance, which serves as a protection to the integu- 

 ment of the nipple during the act of sucking. The nipple consists of numerous 

 vessels, intermixed with plain muscular fibres, which are principally arranged in a 

 circular manner around the base, some few fibres radiating from base to apex. 



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

 lobes ; and of fatty tissue in the intervals between the lobes. The gland-tissue, 

 when freed from fibrous tissue and fat, is of a pale reddish color, firm in texture, 

 circular in form, flattened from before backward, thicker in the centre than at the 

 circumference, and presenting several inequalities on its surface, especially in front. 

 It consists of numerous lobes, and these are composed of lobules connected together 

 by areolar tissue, blood-vessels, and ducts. The smallest lobules consist of a cluster 

 of rounded alveoli, which open into the smallest branches of the lactiferous ducts ; 

 these ducts, uniting, form larger ducts, which terminate in a single canal, correspond- 

 ing with one of the chief subdivisions of the gland. The number of excretory ducts 

 varies from fifteen to twenty : they are termed the tnbitU lactiferi, or galactophori. 

 They converge toward the areola. beneath which they form dilatations, OTampuUw. 

 which serve as reservoirs for the milk, and at the base of the nipple become 

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

 orifices considerably narrower than the ducts themselves. The ducts are composed 

 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 of the mammary gland differs according to the 

 state of activity of the organ. In the gland of a woman who is not pregnant or 

 suckling the alveoli are very small and solid, being filled with a mass of granular 

 polyhedral cells. During pregnancy the alveoli enlarge and the cells undergo 

 rapid multiplication. At the commencement of lactation the cells in the centre 

 of the alveolus undergo fatty degeneration, and are eliminated in the first milk 

 tost rum-corpuscles. The peripheral cells of the alveolus remain, and form 

 a single layer of granular, short columnar cells, with a spherical nucleus, lining 

 the limiting membrana propria. These cells during the state of activity of the gland 

 are capable of forming, in their interior, oil-globules, which are then ejected into 

 the lumen of the alveolus and constitute the milk-globules. 



The librou* f/W- invests the entire surface of the breast, and sends down 

 septa between its lobes, connecting them together. 



The faff >/ tissue surrounds the surface of the gland and occupies the interval 

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

 the form and size of the gland. There is no fat immediately beneath the areola 

 and nipple. (The colostrom-corpuscles may be emigrated white corpuscles.) 



Vessels and Nerves, The arteries supplying the mamma? are derived from the 

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



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

 the cimiliix i-cnosus. From this large branches transmit the blood to the 

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

 The lymphatics, for the most part, run along the lower border of the Pectoralis 

 major to the axillary glands ; some few. from the inner side of the breast, perforate 

 the intercostal spaces and empty themselves into the anterior mediastinal glands. 

 The nerves are derived from the anterior and lateral cutaneous nerves of the thorax. 



