972 OF GENERATION LACTATION. 



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. The inner surface of the milk-folli- 

 cles, in common with other glandular structures, is covered with a layer of 

 epithelium-cells (Fig. 369), as was first observed by Prof. Goodsir ; and 

 these, being seen to contain milk-globules, may without doubt be regarded 

 as the real agents in the secreting process. Absorbent vessels are seen to 

 arise in large numbers in the neighborhood of the follicles; their function 

 appears to be, to absorb the more watery part of the milk contained in the 

 follicles and tubes, ?o as to render it more nutrient than it is when first se- 

 creted ; and also to relieve the distension which would occur, during the 

 absence of the child, from the continuance of the secreting process. 



808. The Mammary gland may be detected at an early period of foetal 

 existence ; being easily distinguishable from the surrounding parts by the 

 redness of its color and its high vascularity, especially when the whole is 

 injected. At this period it presents no difference in the male and female ; 

 and it is not until near the period of puberty that any striking'change mani- 

 fests itself, the gland continuing to grow, in the one sex as in the other, in 

 proportion to the body at large. At about the age of thirteen years, how- 

 ever, the enlargement of the gland commences in the Female; and by six- 

 teen, it is greatly evolved, and some of the lactiferous tubes can be injected. 

 At about the age of twenty, the gland attains its full size previous to lacta- 

 tion ; but the milk-follicles cannot even then be injected from the tubes. 

 During pregnancy, the mammte receive a greatly increased quantity of 

 blood. This determination often commences very early, and produces a 

 feeling of tenderness and distension, which is a valuable sign (where it exists 

 in connection with others) of the commencement of gestation ( 758). A 

 true lacteal secretion usually commences about the third or fourth mouth of 

 pregnancy, and may be obtained by pressure carefully applied. This may 

 be turned to useful account, in diagnosing cases of concealed or doubtful 

 pregnancy from cases of simple suppression of the catamenia ; but it will 

 not serve to distinguish true pregnancy from spurious, or from the distension 

 of the uterus by tumors. 1 The vascularity of the gland continues to increase 

 during pregnancy; and at the time of parturition its lobulated character can 

 be distinctly felt. The follicles are not, however, developed sufficiently for 

 injection, until lactation has commenced. After the cessation of the cata- 

 menia from age, so that pregnancy is no longer possible, the lactiferous 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. 



809. The Mammary gland of the Male is a sort of miniature picture of 

 that 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 corresponds exactly with that of 

 the female, but is altogether formed on a smaller scale. It is composed of 



1 Sec a valuable; paper by D. Peddle, On the Mammary Secretion, in the Edinb. 

 Monthly Journal, Aug. 1848. 



