216 EARL W. FLOSDOKF 



many years; upon reconstitution growth may bo started again to 

 produce subeultiu'es of unaltered characteristics. 



Influenza virus may be successfully preserved (7) and freeze- 

 drying is used widely for carrying various strains of the virus in many 

 research laboratories. Hoffstadt and Tripi (13) report successful 

 three year preservation of Levaditi and Cutter strains of vaccinia, 

 herpes simplex, laryngotracheitis of fowls, and Rous sarcoma viruses. 

 On the other hand, they found inconstant maintenance of viability of 

 the virus of infectious myxomatosis of rabbits over the three year 

 periods; whether this was because of nonuniform residual content 

 of moisture or other cause was not determined. Their culture of OA 

 strain of Shope's fibroma did not survive the period. Other viruses 

 that have been successfully kept are those causing hog cholera {14), 

 rinderpest, ovine ecthyma (sheep scabs), yellow fever, and various 

 fowl diseases such as laryngotracheitis and fowl pox prepared from 

 chick embryos. 



Libby (15) has used freeze-drying in immunochemical studies with 

 tagged antigens involving radiotracers, also with tobacco mosaic 

 virus tagged wdth radioactive phosphorus (P^^). Mice were injected 

 with the tagged virus, 24 hours later the mice were killed in a Dry 

 Ice-acetone bath and 3 to 4 mm. sagittal sections were prepared with 

 a band saw. These sections after freeze-drying were impregnated 

 with paraffin and 1 mm. sections were prepared with a microtome and 

 placed in intimate contact with X-ray film for exposure for varying 

 periods to obtain radioautographs (also see chapter on radioactive 

 isotopes). In this way it is possible to locate regions and organs of 

 greatest concentrations of radioactivitJ^ 



Bacteriophage from many organisms has been dried, including that 

 of dysentery (19). Harris and Shackell used drying in a glass desic- 

 cator for preservation of rabic brains (9). Rivers and Ward have 

 relied widely on freeze-drying in their work with an intradermal vac- 

 cine for Jennerian prophylaxis (10). Siedentopf and Green (11) have 

 reported great success in the preservation of modified canine distemper 

 virus (ferret passage) . 



4. Preservation of Body Fluids and Miscellaneous Products 



As a research tool in the laboratory, freeze-drying oft'ei's many 

 possibilities. The porosity and friability of the dehydrated material 

 makes it particularly adaptable to rapid and sterile extraction with 



