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Fig. 16. Vesicle between two mammary tumor cells. Clump of early particles in right 

 lower area of cytoplasm. Microvilli with virus particles within them projecting into 

 vesicle. (From Bang et al., 1956a) (Magnification: x 18,000). 



Fig. 17. Collection of virus particles in cytoplasm of mammary tumor of mice. Two 

 projecting microvilli are seen in upper left area. (Courtesy Dr. \Y. Bernhard: Bernhard, 

 Guerin, and Oberling, 1956b.) 



