“…In this connexion, the occurrence of antibody to M. fermentans in 13-5 % of adult sera diluted 1/5 is of interest since reports of the isolation of this mycoplasma species from man are few (Huijsmans-Evers & Ruys, 1956;Ruiter & Wentholt, 1953). Recently, 'virus-like' particles associated with human leukaemic bone marrow (Murphy, Furtado & Plata, 1965) have been identified as M. fermentans in this laboratory. In addition to M. fermentans and the Negroni agent, other acid-producing mycoplasmas have been recovered recently in association with human leukaemia and human tumours (Mittelman, Horoszewicz & Grace, 1965).…”