Human mamma.—The position of the human mamma upon the pectoral muscles is too well known to require any detailed account.
The nipples project forwards and outwards with a slight turn upwards, a direction which is beautifully adapted to the position of the infant when lying in its mother's arms; and the abundance of the lactiferous tubes at the lower portion of the breast, as will be more particu larly described hereafter, forms a soft cushion for the head of the child to rest upon.
" The margins of the breast," says SirAstley Cooper,' "do not form a regular disc, but the secreting structure often projects into the sur rounding fibrous and adipose tissue so as to produce radii from the nipple of very unequal lengths, and a circular sweep of the knife cuts off many of its projections, spoils the breast for dissection, and in surgical operations leaves much of the disease unremoved." At the age of puberty and for some time after, if the breasts are not called upon to per form their office, they present to the touch a dense, compact, smooth, and equal surface ; but the distension of the cells in lactation stretches and relaxes the uniting cellular and fibrous membrane, and separates it into "small bodies with indentations around them." This lobulated character does, however, supervene even in childless women upon the cessation of the sexual secretion.
Following the arrangement of Sir A. Cooper, we shall consider the individual parts of the breast from without inwards.
The nipple is not placed in the centre of the breast, but nearer the abdominal margin of the gland. In the virgin it is a rounded cone and nearly smooth until puberty, but in the lactating woman forms a flat surface, cribriform with the lactiferous tubes in the centre. " At 16 years it is slightly wrinkled; at 17 it has small papilla upon its surface; from 20 to 40 years the papilla are large; from 40 to 50 the nipple becomes wrinkled ; from 50 to 60 the nipple is elongated; and in old age it usually has a warty appearance." This alteration in form during lactation, the extremity becoming the broadest part, renders the adhesion of the child's mouth firmer and more complete.
The nipple or mammilla consists of the com mon integuments, fascia, milk-tubes, blood vessels, nerves, and connecting cellular mem brane.
The cuticle offers no peculiarities except the processes which it sends into the lactiferous tubes, which may he drawn out after continued maceration. Its extreme delicacy is well known to the medical practitioner.
Sir A. Cooper states that the rcte mucosuni " enters with the cuticle into the lactiferous tubes." This may be better seen in the larger quadrupeds, where they terminate a few lines from the extremities of the tubes, forming a fringed edge.
" Cutis of the nipple—This forms a consider able portion of the inammilla, and it is divided into two surfaces when the breast is in a state of lactation.
"The first forms the disc or circumference of the nipple, and the second its broad, flat, truncated apex, in which the terminations of the milk-tubes may be seen in numerous orifices.
" The disc is composed of a great number of papilla?, which produce a vascular and sentient surface, and which form its erectile and highly sensitive tissue.
" The direction of these papilla is from the base towards the apex of the nipple, so that they are pushed back as the mammilla enters the mouth of the child, and thus greater excite ment is produced.
" They lap over the truncated extremity of the nipple, forming a foliage upon its apex. This foliated character is one of the consequences of gestation.
" They form in their arrangement upon the nipple broken portions of circles, but when the nipple is elongated and dried they appear to be spiral.
" They form flaps, which are at their edges divided into numerous projections, with serrated depressions between them.
" They are directed forwards towards the apex of the nipple, and the papilla of the child's lips passing from within outwards, meet them in sucking, are received between them, inter mix with them, and produce considerable adhesion and sensation.