. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 148 DEVELOPMENT OF THE SUDORIPAROUS GLANDS ~h whereby it becomes detached from the hair, and the replacing hair arises from a papilla which is probably budded off from the older one before its degeneration and carries with it a cap of epidermal cells. It is uncertain whether the cases of excessive development of hair over the face and upper part of the body which occasionally occur are due to an excessive development of the later hair follicles (hypertrichosis) or to a persistence and continu
. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 148 DEVELOPMENT OF THE SUDORIPAROUS GLANDS ~h whereby it becomes detached from the hair, and the replacing hair arises from a papilla which is probably budded off from the older one before its degeneration and carries with it a cap of epidermal cells. It is uncertain whether the cases of excessive development of hair over the face and upper part of the body which occasionally occur are due to an excessive development of the later hair follicles (hypertrichosis) or to a persistence and continued growth of the lanugo. The Development of the Sudoriparous Glands.—The sudor- iparous glands arise during the fifth month as solid cylindrical out- growths from the primary ridges of the epidermis (Fig. 87), and at first project vertically down- ward into the subjacent dermis. Later, however, the lower end of each downgrowth is thrown into coils, and at the same time a lumen appears in the center. Since, however, the cylinders are formed from the deeper layers of the epidermis, their lumina do not at first open upon the sur- face, but gradually approach it as the cells of the deeper layers of the epidermis replace those which are continually being cast off from the surface of the stratum corneum. The final opening to the surface occurs during the seventh month of development. The Development of the Mammary Glands.—In the majority of the lower mammals a number of mammary glands occur, ar- ranged in two longitudinal rows, and it has been observed that in the pig the first indication of their development is seen in a thickening of the epidermis along a line situated at the junction of the abdomi- nal walls with the membrana reuniens (Schulze). This thickening subsequently becomes a pronounced ridge, the milk ridge, from which, at certain points, the mammary glands develop, the ridge. Fig. 87.—Lower Surface of a De- tached Portion of Epidermis from the Dorsum of the Hand. h
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