Electron Microscope Studies of Normal and Malignant Tissues of High- and Low- Breast-Cancer Strains of Mice

Abstract

THE consistent finding, by means of the electron microscope, of roughly spherical particles of various sizes but mostly of the order of 200–300 A. in diameter in extracts of tumours, lactating breast tissues, and other tissues of high-breast-cancer-strain mice and their absence in low-breast-cancer strains was reported in Nature two years ago¹; and shortly afterwards² it was reported that similar particles were to be found in extracts of milk of the C3H high-cancer strain. In the latter communication, it was further shown that it was possible by ultra-centrifugation of tumour extracts to obtain a supernatant apparently free from particles, and it was also reported that the test hybrid mice inoculated with particle-containing extracts described in the first communication had developed mammary tumours, indicating that such extracts were biologically active.