Experimenters1 in the Rockefeller Institute observed two decades ago that tubercle bacilli ingested by leukocytes are apparently protected from the lytic action of the peritoneal antibodies of tuberculo-immune guineapigs. This immunologic paradox was afterward studied in detail by Rous and Jones,2 who found that test tube phagocytosis not only protects such micro-organisms as the typhoid bacillus against lysis by homologous specific immune serums but also protects them against certain chemical antiseptics. This protection is apparently due to certain vital factors in the ingesting phagocytes, since cytologic protection ceases on the death of these cells. The New York investigators concluded from their data that serum therapy and chemotherapy might conceivably be ineffective in numerous specific infectious diseases, solely on account of the intracellular location of the infectious agent.
Rous and his colleagues3 have recently extended this paradox to include certain filtrable viruses. Suspensions of embryonic tissue culture cells