Negative results of attempts to prolong the effect of phospholipids (PL) and cholesterol (Chol) on the formation fo tumours induced by 3-methyl-cholanthrene (MeC).

It was formerly demonstrated that PL retard and Choi accelerates the formation of tumours induced by M e C 2. This retardation respectively acceleration, however, never surpassed a period of somewhat more than four weeks. The question, then, arose why PL are only capable to retard temporarily and not to pre­ vent, i. e. retard permanently, the formation of tu­ mours. It was presumed that the administration of an excess of PL could favourably influence the time of re­ tardation, namely by impeding the liberation of MeC from its molecular associations with PL through the interaction of Choi occurring everywhere in the or­ ganism : PL-MeC + Choi PL-Chol + MeC.