I.—On the Developmental Processes in Mammary Glands and other Epidermal Structures

Abstract

Synopsis: The early development of the mammary glands and of hair follicles in the mouse and the rabbit has been investigated by means of mitotic counts, by histochemical methods and by cultivationin vitro. In the first stage of the formation of both types of rudiment a thickening of the epidermis appears as a consequence of an aggregation of cells, not of a local elevation of the mitotic rate. During this stage alkaline phosphatase is absent from the cells and the content of ribose-nucleic acid reduced. Both these substances appear in higher concentrations later, and their relation to processes of growth and differentiation is discussed. Essentially similar phenomena are found in rudiments cultivatedin vitro, which, however, frequently suffer a degeneration by a process of keratinisation.