Abstract
Summary
When the concentration of virus in stock filtrates of the tissue culture fluids was greater than 10 6 TCD50 per ml, membranes with an APD of 39 mμ to 44 mμ allowed a certain proportion of poliomyelitis virus particles to pass. Membranes with an APD of 36 to 39 mμ held back the virus and, according to Elford's formula, the size of all 3 types of poliomyelitis virus is estimated at 12-20 mμ. After removal of gross amorphous material by preliminary centrifugation, the tissue culture fluids yielded practically pure suspensions of virus particles which measured, on the average, 30 mμ for Type 1 (Mahoney), 27 mμ for Type 2 (Y-SK), and 41 mμ for Type 3 (Leon). The seemingly larger size of the Type 3 particles may be an artifact.
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