Variation of the mammary glands response of inbred female mice treated with estrogen.

It has been widely accepted that inbred strains of mice and other rodents should be used for experimental purposes because such strains are considered to show physiological uniformities with themselves. On the other hand, it has been questioned whether inbred strains of mice are indeed more suitable for experimental purposes. Emmens(1939)found an inbred strain of Strong's CBA mice to be more variable than a randomly bred colony. In 1954, Gruneberg directed attention to evidence that pure lines of mice are much less homogeneous genetically than is generally believed, with reference to the skeletal variation. McLaren and Michie(1954)and Biggers and Claringbold(1954)suggested that inter-strain F1 hybrids were to be preferred to inbr, cd strain of mice for bio-assy. As the first step in an investigation on how genetic factors affect the mamary growth, one of the factors influencing dairy performance,and whether it is possible to control this character by selection, the present study was carried out to investigate the variation of the mammary response of inbred immature mice treated with estrogen and to compare the variabilities of the mammary response of established inbred strains of mice with those of mice bred randomly and inbred for short time.