It is well known that most viral agents lose some of their viability-often rapidly-if stored in ordinary diluents such as buffered saline or nutrient broth. It is also known that this loss of viability is usually dependent on the temperature at which the preparation is stored. The effect of temperature on the storage of certain neurotropic viruses was studied by Olitsky et al. (1950) who found that in the presence of normal rabbit serum at -25 to -30 C most of these agents could be recovered on

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... animal passage after 9 to 12 months storage, though the titers were markedly reduced. Horsfall (1940) has shown that at -70 C most viruses retain their infectivity for long periods of time. Many investigators have shown that some substances, particularly proteins, have a stabilizing or protecting effect on viruses, rickettsiae, and bacteria when used as the suspending menstruum for these agents. Anderson (1944) and Topping (1940) have found sterile skim milk an ideal medium in which to store or lyophilize certain rickettsiae. Dick and Taylor (1949) found that higher infectivity titers were obtained with some viruses, including the virus of yellow fever in the presence of small concentrations of bovine albulmin. Cook and Hudson (1937) and Bauer and Mahoffy (1930) have shown that the presence of some types of serum in the suspending medium has a protective effect on the viruses of yellow fever and St. Louis encephalitis. Bovarnick, Miller, and Snyder (1950) , while looking for a defined medium in which to study purified preparations of rickettsiae, have shown that a medium made up of glutamate high in potassium ion and containing a small amount of serum albumin favored the survival of those strains of rickettsiae studied. When working with a viral agent in the laboratory it is desirable to find an easily prepared medium and the optimal temperature which favor the maintenance of the viability or infectious property of that agent. In our experience, the problem of preservation of members of the psittacosis-lymphogranuloma venerum group and herpes simplex virus was especially critical. It is the purpose of this report to describe the effect of several conditions of storage on the preservation of infectivity of meningopneumonitis and herpes simplex viruses. No 1 USPHS Research Fellow of the National Institutes of Health. These studies were conducted under a contract with the Office of Naval Research. 369 on May 7, 2020 by guest