The Effect of Testicular Extract on Filterable Viruses

The Reynals factor promotes the pathogenic action of the viruses of herpes, vesicular stomatitis of horses, Borna disease, and vaccinia. The heightening of virulence is revealed in various ways. The effects of the viruses may be accentuated; or a weak strain converted into a strong one, as in the case of the F. strain of herpes virus; or the power acquired to infect resistant species or tissues, as, e.g., rabbits and the abdominal skin of guinea pigs, with acute vesicular stomatitis. The Reynals factor should serve as an important agent in the study of filterable viruses.