“…According to previous studies, the inhibitor concentration in plasma is too small to use antigcn-antibody precipitation reactions (Denson, 1967;McLester et af, 1965). Furthcrmore, the results of such attempts have been questioned (Penalver et al, 1957;Ehrenworth, 1963 ;Denson, 1967;Bidwell, 1966;Berglund, 1963). Passive haemagglutination as used by several authors (Colombani & Tcrricr, 1962;Roberts et al, 1965) was found unsuccessful in our case as well as in previous studies (Biggs & Bidwell, 1959;Ratnoff, 1957).…”