A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . nds with the number of excretoryducts which the mature glands will possess. Theupper ends of the plugs are in the nipple zone, butthe greater part of their lower ends project into theloose connective tissue of the cutis. Only some of these sprouts are held by Eggeling torepresent the ducts of the mammary glands whosegrowth forms the parenchyma of the glands. Othersare very early anlages of hair and still others anlagesof sebaceous glands. Neither of these complete
A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . nds with the number of excretoryducts which the mature glands will possess. Theupper ends of the plugs are in the nipple zone, butthe greater part of their lower ends project into theloose connective tissue of the cutis. Only some of these sprouts are held by Eggeling torepresent the ducts of the mammary glands whosegrowth forms the parenchyma of the glands. Othersare very early anlages of hair and still others anlagesof sebaceous glands. Neither of these complete theirdevelopment and become hair or sebaceous glandsbut join in the lactiferous duct. REFERENXE HAXDBOOK OF THE MEDICAL SCIENCES Breast, Anatomy of There is now developed a new zone beneatli thenipple zone, composed of voung, round, closelypacked connective-tissue cells. Surrounding andsupporting the epithelial elements of the gland, theseform the stroma of the giand (stroma zone). A retrograde metamorphosis begins in thecentral cells of the primary epithelial ingrowth, andfrom the center the degeneration proceeds per-. Fig. 1092.—Primitive Xipple of a 12 cm. Pig Embryo with an Epithelial Sprout (sp).cw. Cutis wall: mt, mammary point. (For other letters, see Figs. 1090 and 1091.) ipherally and downward. It takes the form of acornification (Fig. 1093, hp) and proceeds at first veryrapidly, though its final progress is so slow thatsometimes it is not complete until after ;ately it leads to the complete disappearanceof the primary epithelial ingrowth or mammarypoint. At the same time as the primary, ingrowth is de-generating the secondary ingrowth, nipple zone, andstroma zone are continuing to develop. As thesecondary epithelial plugs push their way into theunderlying mesodermic stroma, they become club-bed below. At the same time the originally solidplugs are hollowed out and converted into tubes,and during the seventh month of intrauterine life,or about that t
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