Attempts at Oral Transmission of Mammary Tumour Agent by Feeding Male Organs

THE male mouse harbours the mammary tumour virus in its testes, spermatozoa vesicular glands and fluid (Andervont and Dunn, 1948; Miihlbock, 1950) as well as in other sites. Male secretions therefore might be a source of infection to female offspring either by direct contact or by infection of their mothers. Miihlbock (1952a) suggests that repeated copulation by increasing the mammary agent transmitted by a " high cancer " male to a " low cancer " female eventually leads to a high enough concentration of agent for the mother to transmit it to her young in the milk. He also injected extracts of embryos removed from high cancer strain mothers with mammary tumours into 3 to 4 weeks old susceptible mice (Muhlbock, 1952b). These mice did not develop any mammary tumours, in spite of being force-bred; while 50 per cent of mice injected with placental extracts from a similar source developed mammary tumours. Though these experiments do not exclude absolutely the contamination of the young through the placenta, they support the concept of indirect infection by the mothers' milk. The possibility remains that unexplained mammary tumours might be due to chance oral contamination of the offspring in the cage when coming into contact with some secretion of its male parent In the human subject the mumps virus localises in the mammary gland, parotid and testes, and this association suggested that a similar tropism for these glands may exist in the case of the mammary tumour agent in mice. In the following experiments it was proposed to test the possibility of contamination by salivary, testicular or vesicular gland secretions.