EN
In two experiments 11 cows were given intravenously or intramammarily 10 and 15 per cent suspensions of sheep red blood cells (SRBC). Plaque-forming cells (PFC) from blood and milk were determined by the Jerne technique modified by Sterzl et al. It was found that PFC appeared in blood and milk both after intramammary and intravenous inoculations of the antigen. The number of PFC was usually greater in that fluid to which SRBC were introduced. This suggests the local origin of the PFC. After inoculation of a 15 per cent suspension of erythrocytes, the PFC appeared later and remained longer in the fluids examined.