Colon bacilli, Virus III, vaccine virus, herpes virus, bacteriophage, complement, and trypsin are either killed or inactivated by repeated freezing (–185°C.) and thawing. As might be expected, some of the agents are more resistant than others.

Hence it may be concluded that destruction or inactivation of an active agent by repeated freezing (–185°C.) and thawing is not proof that it was possessed of life.

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