" But the absorbents of the concave or costal surface of the breast take a different course. They penetrate the intercostal muscles behind the breast and enter absorbent vessels which accompany the aortic intercostal arteries on the axillary side of the breast, but on the sternal side they join the internal mammary inter costals ; the former pass into the thoracic duct in the posterior mediastinnm ; the latter enter those vessels in the anterior mediastinum which I have already described." The effect of age upon the mamma is to absorb its glandular structure, to load the ducts with mucus, to obliterate the milk cells, to excessively ossify the arteries, and to thin and wrinkle the nipple, and at length in a great degree to absorb it. But the deposition of fat occupying the place of the glandular structure, the general contour of the breasts in fat persons is maintained.
On the mammary glands in the male.--The credit of discovering the intimate structure of this gland in the male is entirely due to Sir Astley Cooper ; nothing, we believe, what ever having been known on the subject pre vious to his researches. Its size varies in different individuals ; it is largest in men of light complexion and effeminate appearance. " The largest male glands which I have seen," says this author, " were found in a man whose testes were remarkably small." In some persons it is no bigger than a large pea, in others an inch and a half or even two inches. There are papilla on the nipple and in the areola of the male as in the female, only they are more minute and much less vascular. The cutaneous glands and tubercles are very similar in both sexes.
" The gland is constituted of two parts :— first, of very minute cells, and, secondly, of small conical ducts which divide into nume rous branches in the glands, and terminate in straight ducts which end in very minute orifices at the nipple. In their form, in their divi sions, and in their course through the nipple, they all form a miniature resemblance of the gland and vessels of the mammary gland in the female." (Fig. 76.) The whole is sup ported by a firm fascia, as in the female.
Murat and Patissier, in the article Mamma,* refer to a case related by Dr. Renault of an individual whose mamma: were equal in size to those of the female and emitted a serous fluid having the appearance of milk. The organs of generation were diminutive, the testicles about the size of a small nut, and his penis like a mere tubercle, and, even in a state of erection, only an inch and a half in length. Neverthe less he was given to venereal intercourse and all the usual habits of men.
This discovery of the glandular structure of the male breast explains, most satisfactorily, the cases which are on record of the sustenance of the infant by the male parent after the death of the female, the most authentic of which is related by Humboldt in his travels.t Although the usual number of mamma in the human species is only two, still there are exceptions and instances on record of more having been developed. One of the
best authenticated and most recent of these cases is related by Dr. Lee, in the Transac tions of the Medical and Chirurgical Society for 1837.* In this instance " the inferior or pectoral mamma were fully developed and in the na tural situation, and their nipples, areola, and glands presented nothing unusual in their ap pearance. Near the anterior margin of the axilla, a little higher up on each side, was si tuated another mamma, about one-sixth of the size of the others. The nipples of these were small and flat, but when gently pressed, a milky fluid which had all the external cha racters of the milk secreted by the other breasts, flowed copiously and readily from several ducts which opened on their extremities. When milk was drawn from the lower breasts, a small quantity usually escaped from the nipples of the superior breasts, and when the draught came into the former, the latter invariably be came hard and distended." The flatness of the nipples prevented her suckling her children by them. Dr. Lee, in the above paper, quotes five other cases from foreign authors of qua druple mamma, also stating that " in some women only one breast has been developed ; others have had two nipples placed on one mamma; and a few individuals have had three breasts, two in the natural situation and a third situated in the middle of the two others. Only one case has been recorded of five mamma in the human subject."t Comparative anatomy.—In considering this division of our subject we shall especially di rect our attention to those points in the anatomy of the mamma of animals which possess a phy siological interest, omitting minute anatomical details unless they bear upon general principles. These organs in the Kangaroo, one of the Mar supiata, as we have already hinted at, are peculiarly formed, for the young of these ani mals,wben first removed from the uterine cavity of its parent, is more like an earth-worm in its appearance than the active animal by which it is produced. So helpless is the condition of this young animal that it has not been inap propriately called a mammary fiat% for the mamma, in this instance, act at first like a true placenta as a permanent conductor of nutri ment, and not, as in the higher Mammalia, a mere storehouse to be resorted to occasionally. Indeed, so close is the union between the pa rent and its offspring, and so imperfect the power of the foetus to abstract nourishment by suction, that Geoffroy St. Hilaire had recourse to the hypothesis that there was some vascular connexion. But the imperfect power of the foetus is compensated by the addition to the breast of a muscular apparatus, which propels forwards the nutritious juices of the mother into the alimentary cavity of the helpless young one. From the interesting account which Mr. Morgan has given of these glands* in the Kangaroo, we shall extratl the following particulars.