Hormonal synergism in mammary growth

Abstract

Much of this report will consist of a summary of the mammary work done in the Department of Anatomy during the past 25 years in collaboration with Professor H. M. Evans’s group in the Institute of Experimental Biology and Professor Choh Hao Li of the Laboratory of Hormone Research, all of the University of California. Such a summary may be made most conveniently by using a schema and some photographs representing our main findings in the Long-Evans rat. The more difficult task is to fit this research into proper perspective involving, as it must, some reference to a mass of literature on the mammary gland. Rather than attempt a thorough review of the thousands of papers in this field, relatively few key examples have been chosen to indicate the trend of thought and theory during and just preceding the period of our investigations. For more complete reviews on this subject the reader is referred to Mayer & Klein (1948, 1949), Cowie & Folley (1955) and Folley (1956). Of historical interest is de Rothschild’s (1900) list of about 10 000 references to the literature prior to 1900, with supplements in 1901 and 1902. If a quarter of a century seems a long time to be engaged in elucidating the problem of hormonal control of the mammary gland, some explanation may be found in the fact that this was the period of isolation of the many hormones involved, and of developing satisfactory techniques for multiple endocrinectomies. That the problem would become a complicated one might have been suspected from the knowledge that the mammary gland arrived late, if not last, in the phylogenetic scale of organ evolution. Further, proof that such suspicion was well founded has been adduced in the many experiments showing that the main phases of mammary growth and function are dependent upon all of the hypophysial hormones and their target organ hormones, plus the secretions of that latest arrival on the endocrine scene—the placenta.