4eG THE MAMMARY GLANDS. 



MAMMARY GLANDS. 



The mammary glands (mammas), -which yield the milk in the female, 

 are accessory parts to the reproductive system. They give a name to a 

 large class of animals (Mammalia), which are distinguished by the pos- 

 session of these organs. When fully developed in the human female, 

 they form, together with the integuments and a considerable quantity 

 of fat, two rounded eminences (the breasts) placed one at each side on 

 the front of tlie thorax. These extend from the third to the sixth or 

 seventh rib, and from the side of the sternum to the axilln. A little 

 below the centre of each breast, on a level with the fourth rib, or a 

 ittle lower, projects a small conical body named the nipple (mammilla), 

 which points somewhat outwards and upwards. The surface of the 

 nipple is dark, and around it there is a coloured circle or areola, within 

 which the skin is also of a darker tinge than elsewhere. In the virgin, 

 these parts are of a rosy pink colour, differing somewhat according to 

 the complexion of the individual, and they are always darker in women 

 who have borne children. Even in the second month of the first preg- 

 nancy, the areola begins to enlarge and acquire a dai'ker tinge ; these 

 changes go on increasing as gestation advances, and are regarded as- 

 signs to be relied on in judging of suspected pregnancy. After lactation 

 is over, the darlc colour subsides, but never entirely disappears. The 

 skin of the nipple is marked with many Avrinkles, and is covered with 

 papilla3 ; besides tliis, it is perforated at the tip by numerous foramina, 

 which are the openings of the lactiferous ducts : and near its base, as 

 well as upon, the surface of the areola, there are scattered rounded ele- 

 vations, which are caused by the presence of little glands with branched 

 ducts, four or five of which open on each elevation. The tissue of the 

 nipple contains a large number of vessels, together with much plain 

 muscular tissue, and its papilla are highly sensitive ; it becomes firmer 

 and more projecting from mechanical excitement, — a change mainly 

 caused by contraction of the muscular filires, which form concentric 

 circles round the base, and some radiating bands running from base to 

 apex of the nipple. 



The base of the mammary gland is somewhat oval, flattened, or 

 Slightly ccmcave, and has its longest diameter directed upwards and 

 outwards towards the axilla. The gland lies in connective tissue con- 

 tinuous with the superficial fascia, its base resting on the pectoral 

 muscle, and separated from it by a layer of firm areolar tissue con- 

 tinuous with the deep fascia. The thickest part of the gland is near the 

 centre, opposite the nipple. 



On the surface, and penetrating also between the lobes, there is a 

 large quantity of fat, which mainly gives the full and smoothly rounded 

 form to the gland. This fat is of a firm consistence and bright yellow 

 colour, and is subdivided into lobules by partitions of connective tissue. 

 It is entirely absent from the nipple and areola. 



STRUCTURE OF THE MAMMA. 



The glandular substance of the mamma consists of numerous distinct 

 lobes held together by firm intervening fibrous or areolar tissue, and 



