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May 6, 1939


JAMA. 1939;112(18):1832. doi:10.1001/jama.1939.02800180056017

The cultivation of a barely visible filtrable pleuropneumonia-like virus1 from human rheumatic exudates and proof of its pathogenicity for laboratory animals has been reported recently by Swift and Brown2 of the Rockefeller Institute. The chorio-allantoic membranes of chicken embryos were inoculated with joint exudates. Characteristic pearl-like lesions developed on the egg membranes, "globular structures surrounded with flattened epithelium but containing in their center condensed eosinophil material." As many as twenty-four serial passages of the nodule-producing virus were made. During this process an occasional egg became contaminated with ordinary bacteria. Contaminated egg membranes emulsified in 10 per cent human serum were readily freed from all ordinary bacteria by Berkefeld filtration. The resulting filtrates showed little or no reduction in nodule-producing virus titer.

By the Sabin method of "blind passages"3 in beef-serum-dextrose-broth the investigators eventually succeeded in growing a minute, barely visible, pleomorphic micro-organism from such filtrates and directly