In 1935 Schlesinger1 found that deposits obtained by high speed centrifugation of pericardial fluids from cases of acute rheumatism contain minute bodies which in their size and shape resemble virus particles. Relatively pure suspensions of these particles were agglutinated by serums from acute rheumatic patients. They were not agglutinated by normal human serum or by the serum of patients suffering from nonrheumatic disease. Schlesinger did not challenge prevailing belief in the importance of hemolytic streptococci in acute rheumatic infections. He concluded that streptococcic infections lower normal resistance to the rheumatic cardiotropic virus or otherwise activate this virus.
Tests of the pathogenicity of the presumptive rheumatic virus are now reported by MacNeal and his associates2 of New York Post-Graduate Medical School. In a typical experiment a specimen of pericardial fluid from a patient who had died of acute rheumatic carditis was passed through a Mandel filter. The bacteriologically sterile