"The study of epidemiology of the mouse leukemia virus is of considerable importance since it may lead to the understanding of the spread of this disease in nature."
With this cautious prologue, Ludwik Gross, MD, chief, Cancer Research Unit, Veterans Administration Hospital, Bronx, NY, traced how the virus is passed from mouse to mouse under natural life conditions.
Speaking at the M. D. Anderson Symposium on Fundamental Cancer Research, Dr. Gross made no further reference to the growing debate over whether an analogous infectious agent or method of transmission may play a part in human leukemia. Instead, he reported his own experiments and reviewed those of other investigators which indicate the mouse leukemia virus:
Follows a principal path of vertical transmission, from generation to generation within certain families of mice;
May, rarely, be transmitted horizontally by contact among new-born mice. "However, the infection acquired in this manner may not be