THE MAMMARY GLANDS. 1147 
also the areola increases in size and its glands become more marked. The nipple 
contains a considerable number of unstriped muscle fibrés, and becomes firmer and 
more prominent as a result of mechanical stimulation. 
The size and appearance of the mammary glands vary much, not only in the 
different races of mankind, but also in the same individual under different conditions, 
In the young child the mamme are small, and there is little difference in the male 
and female. Their growth is slow until the approach of puberty, and then the 
female mamme increase 
rapidly in size. At each pree- 
nancy the mamme become 
large, and they attain their 
greatest development during 
lactation. The size of the 
mamma depends partly on the 
amount of superficial fat and 
partly on the amount of gland- 
ular tissue present. 
Structure of the Mamma. 
—The mamma is composed of 
amass of glandular tissue tra- Ducts 
versed and supported by 
strands of fibrous connective 
tissue, and covered by a thick oid 
layer of fat. The glandular 
tissue,to which the term corpus 
mammez is applied, forms a 
somewhat conical mass whose Fic, 784,—DIssECTION OF THE MAMMARY GLAND. 
apex corresponds to the position 
of the nipple, while its base is loosely connected to the fascia coy ering the pectoralis 
major. In section the corpus mamimee is readily distinguished from the surr rounding 
fat by its firmer consistency and by its pinkish- white colour. The corpus Mammee 1s 
composed of lobes and lobules, and its superficial aspect and edges are very uneven 
—the inequalities of its surface being tilled up by processes of the fatty tissue which 
forms a covering for the gland. This covering is incomplete beneath the areola, 
where it is pierced by the lactiterous ducts as they pass into the nipple. The gland 
is composed of fifteen to twenty lobes (lobi mamme.) which radiate from the nipple, 
each lobe being quite distinct from the others and possessing its own duct. The 
lobes are subdivided into secondary lobes and lobules, bound together and supported 
by a considerable amount of connective tissue which forms the stroma of the eland. 
The alveoh of the gland and the secretory epithelium lining them vary ‘much 
under different conditions. At puberty the corpus mammee is chiefly composed. of 
connective-tissue stroma and the ducts of the gland. At this time the alveoli are 
small and few in number. During lactation, when the gland is fully functional 
the alveoli are enlarged, distended with fluid, and much more numerous. The 
epithelial cells are cubical and filled with fat globules. When the gland is not 
secreting the alveoli become small and reduced in number, while the ‘cells of the 
lining epithelium, which are now small and granular, do not contain fat globules. 
The duct (ductus lactiferi) of each lobe, passing towards the nipple, becomes 
enlarged to form a small spindle-shaped dilatation called an ampulla or sinus lactiferi ; 
then ‘Decoming once more constricted, it passes, without communicating with the 
other duets, to the summit of the nipple, where it opens. 
In the male subject the various parts of the mamma are represented in a rudi- 
mentary condition. 
The presence of milk glands is characteristic of the clgss mammalia, and the 
number of pairs of olands in each group of animals bears some relation to the 
number of young usually produced at each birth. 
Ampulla 
Variations—Asymmetry in the development of the mammée is very common—the left 
mamma being very often larger than the right. Absence of one or both mamme is a very 
rare abnormality, which may or may not be associated with absence of the nipples. When one 
