THE MAMMA.
Position and Shape.
They are two in number, placed on the anterior and superior part of the chest, on the right and left of the sternum, in front of the pectora lis major, and in the space between the third and seventh rib.
Rudimentary in man and little girls, they develop to the time of puberty, increasing in size during pregnancy, and attain their greatest development after confinement, under the influence of the secretion of milk. Their size is extremely variable in different women, and especially in different races. The left breast is often larger than the right.
The gland is generally hemispherical, but often has a conical or discoid shape. Their shape is greatly changed in aged or thin wotnen, and more than all in women who have nursed.
Their external surface has three distinct zones: a white peripheral part, smooth, soft and yielding to the touch, a middle part which forms the areola, and a central projecting part, the nipple.
The areola is rosy in young girls, and is colored in pregnant women. This color is generally the same as the color of the hair. Next to nothing in blondes, this coloration increases in brown-haired women, and some times becomes very deep in brunettes. This coloration divides the areola into two parts—one central, the true areola, and the other eccentric, surrounding the latter. This is the secondary areola, which is mottled or spotted. We will return to this when we study the changes in the geni tal organs caused by pregnancy.
The skin of the true areola contains a large number of sebaceous glands; also, a dozen or twenty projecting tubercles which, according to some writers, are only sebaceous glands, to others (Depaul), true rudi mentary nipples, from which it is easy to extract a liquid which shows, under the microscope, all the characteristics of milk. Sappey ex plains this from the fact that each of these sebaceous tubercles is crossed by a little galactophorous duct coming from a supplementary lobule con nected to the gland. (Figs. 54 and 55.) The deep surface of the areola is lined with a layer of muscular fibres placed in a circle around the areola, forming a true orbicular muscle —whence the peculiar retractile power of the areola.
At the centre of 'the areola is the nipple, shaped like a conoid or cylindrical projection, with a round end. It is from .35 to .42 of an inch high, and about .39 inches wide, but its form and size vary greatly in different women. In some cases it sinks into the areola and recalls the arrangement of the umbilicus. Its surface is covered with highly developed papillae, so developed and so compact that in some women the nipple has a true muriform appearance. Below the skin of the nipple is a connective tissue of elastic and muscular fibres, analogous to that of the areola. It is crossed from its base to its apex by galactophorous ducts which open at its free end.
The posterior surface of the mamma is a plane. A cellulo-fibrous lamina covers it and separates it from the lis major, to which it adheres by a loose cellular tissue.
Its circumference is encircled by a cellulo-fatty layer, which forms its principal means of support.
Structure of the The breast consists of skin, the cellulo-fatty layer that lines it, and the mammary gland.
The skin of the peripheral part has the same structure as the skin of the trunk. It contains hair follicles, rudimentary sebaceous glands, and muscular fibres, which are attached to their inferior part, and which contain the glands. It rests on a cellulo-fatty layer which holds it like a cushion.
The areolar part is smaller and more delicate. Its derma consists en tirely of fibres of connective tissue and of elastic fibres. It contains hair follicles, sebaceous glands, sudoriparous glands, and its internal surface adheres to a sub-areolar orbicular muscle.
Mammary is situated below these parts in a fold of the fascia superficialis. It forms a hard mass, thicker in the centre than at the periphery. It is composed of 15 or 20 lobes separated from each other by a fibrous covering and by adipose tissue. Each lobe is sub divided into lobules, which are only the union of the acini enlarged at their end. (Fig. 56). From each acinus springs a canaliculus which unites with neighboring canaliculi. The ducts of the lobules unite in their turn and form, finally, the galactophorous ducts. There are 15 to 20 of them.