614 MAMMARY GLANDS. 



of the vagina, which is bounded on each side by the upper portions 

 the nymphae, is the vestibule. 



At the upper angle of the vagina is an elevation formed by the pro- 

 jection of the upper wall of the canal, and analogous to the bulb 

 of the urethra of the male: and immediately in front of this tubercle, 

 and surrounded by it, is the opening of the urethra, the meatus 

 urinarius. 



MAMMARY GLANDS. 



The Mammce are situated in the pectoral region ; and are separated 

 from the pectoralis major muscle by a thin layer of superficial fascia. 

 They exist in the male as well as in the female, but in a rudimentary 

 state, unless excited into growth by some peculiar action, such as the 

 loss or atrophy of the testes. 



Their base is somewhat elliptical, the long diameter corresponding 

 with the direction of the fibres of the pectoralis major muscle ; and the 

 left mamma is generally a little larger than the right. 



Near the centre of the convexity of each mamma is a small pro- 

 jection of the integument, called the nipple., which is surrounded by an 

 areola having a coloured tint. In the female before impregnation, the 

 colour of the areola is a delicate pink ; after impregnation it assumes a 

 brownish hue. which deepens in colour as pregnancy advances ; and 

 after the birth of a child, the brownish tint continues through life. 



The areola is furnished with a considerable number of sebaceous 

 follicles, which secrete a peculiar fatty substance for the protection of 

 the delicate integument around the nipple. During suckling these 

 follicles are increased in size, and have the appearance of small 

 pimples, projecting from the skin. At this period they serve by their 

 increased secretion to defend the nipple and areola from the excoriating 

 action of the saliva of the infant. 



In Structure, the mamma is a conglomerate gland, and consists of 

 lobes, which are held together by a dense and firm areolar tissue ; the 

 lobes are composed of lobules ; and the lobules, of minute caecal 

 vesicles, the ultimate terminations of the excretory ducts. 



The excretory ducts (tubuli lactiferi), from ten to fifteen in number, 

 commence by small openings at the apex of the nipple, and pass 

 inwards, parallel with each other, towards the central part of the gland, 

 where they form dilatations (ampullae), and give off numerous branches 

 to ramify through the gland to their ultimate terminations in the 

 minute lobules. 



The ducts and csecal vesicles are lined throughout by a mucous 

 membrane, which is continuous at the apex of the nipple with the 

 integument. 



In the nipple the excretory ducts are surrounded by a tissue ana- 

 logous to the dartos of the scrotum, to which the power of erectility of 

 the nipple seems due. There is no appearance of any structure re- 

 sembling erectile tissue. 



