MAMMARY GLANDS SECRETION OF MILK. 649 



pricked in paper by the point of a very fine pin; so that the follicles are, when distended 

 \vitli quicksilver or milk, just visible to the naked eye. At other times, however, the follicles 

 do not admit of being injected, though the lactiferous tubes may have been completely filled. 

 They are lined by a continuation of the same membrane, with that which lines the ducts; 

 and this possesses a high vascularity. The arteries which supply the glandules with blood, 

 become very large during lactation; and their divisions spread themselves minutely on the 

 follicles. From the blood which they convey, the milk is secreted and poured into the 

 follicles, whence it flows into the ducts. From the researches of Mr. Goodsir it appears, 

 that, in common with other glandular structures, the inner surface of the milk-follicles is 

 covered with a layer of epithelium-cells; which, being seen to contain milk-globules, may 

 be without doubt regarded as the real agents in the secreting process. Absorbent vessels 

 are seen to arise in large numbers in the neighbourhood of the follicles; their function ap- 

 pears to be, to absorb the more watery part of the milk contained in the follicles and tubes, 

 so as to render it more nutrient than it is as first secreted ; and also to relieve the distention 

 which would occur, during the absence of the child, from the continuance of the secreting 

 process. 



c. The Mammary gland may be dejected at an early period of fetal existence ; being 

 easily distinguishable from the surrounding parts, by the redness of its colour and its high 

 vascularity, especially when the whole is injected. At this period it presents no diiference 

 in the male and female ; % and it is not until near the period of puberty, that any striking 

 change manifests itself, the gland continuing to grow, in each sex, in proportion to the 

 body at large. About the age of thirteen, however, the enlargement of the gland com- 

 mences in the Female; and by sixteen years, it is greatly evolved, and some of the lactife- 

 rous tubes can be injected. At about the age of twenty, the gland attains its full size 

 previous lo lactation ; but the milk follicles cannot even then be injected from the tubes. 

 During pregnancy, the mammas receive a greatly-increased quantity of blood. This deter- 

 mination often commences very early, and produces a feeling of tenderness and distention, 

 which is a valuable sign (where it exists in connection with others) of the commencement 

 of gestation. The Areola at this time becomes darker in its colour, and thicker in sub- 

 stance, and more extended; its papilla become more developed, and the secretion from its 

 follicles increased. The vascularity of the gland continues to increase during pregnancy; 

 and at the time of parturition, its tabulated character can be distinctly felt. The follicles 

 are not, however, developed sufficiently for injection, until lactation has commenced. After 

 the cessation of the catamenia from age, so that pregnancy is no longer possible, the lactife- 

 rous ducts continue open, but the milk follicles are incapable of receiving injection. The 

 substance of the glandules gradually disappears, so that in old age only portions of the ducts 

 remain, which are usually loaded with mucus; but the place of the glandules is commonly 

 filled up by adipose tissue, so that the form of the breast is preserved. Sir A. Cooper 

 notices a curious change, which he states to be almost invariable with age, namely, the 

 ossification of the arteries of the breast, the large trunks as well as the branches ; so that 

 their calibre is greatly diminished, or even obliterated. 



d. The Mammary gland of the Male is a sort of miniature picture of dial of the female. 

 It varies extremely in its magnitude, being in some persons of the size of a large pea ; 

 whilst in others it is an inch, or even two inches in diameter. In its structure it corre- 

 sponds exactly with that of the female, but is altogether on a smaller scale. It is composed 

 of lobules containing follicles, from which ducts arise; and these follicles and ducts are not 

 too minute to be injected, although with difficulty. The evolution of the gland goes on pan 

 passu with that of the body, not undergoing an increase at any particular period; it is some- 

 times of considerable size in old age. A fluid, which is probably mucus, may be pressed 

 from the nipple in many persons ; and this in the dead body, with even more facility than in 

 the living. That the essential character of the gland is the same in the male as in the female, 

 is shown by the instances, of which there are now several on record, in which infants have 

 been suckled by men. The following is given by Dr. Dunglison.* "Professor Hall, of the 

 University of Maryland, exhibited to his Obstetrical class, in the year 1837, a coloured man, 

 fifty-five years of age, who had large, soft, well-formed mammae, rather more conical than 

 those of the female, and projecting fully seven inches from the chest; with perfect and large 

 nipples. The glandular structure seemed to the touch to be exactly like that of the female. 

 This man had officiated as wet-nurse, for several years, in the family of his mistress ; and 

 he represented that the secretion of milk was induced by applying the children entrusted to 

 his care to the breasts during the night. When the milk was no longer required, great dif- 



* Dunglison's Physiology, [sixth ed., vol. ii. p. 480.] See also the case described by the 

 Bishop of Cork, in the Philosophical Transactions, vol. xli. p. 813: one mentioned by Cap- 

 tain Franklin (Narrative of a Journey to the Polar Sea, p. 157); and one which fell under 

 the notice of the celebrated traveller Humboldt (Personal Narrative, vol. iii. p. 58). 

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