Plant Hemagglutinins with Special Reference to a Preparation from The-navy Bean.*

Since the discovery of ricin by Kobert in 1887, considerable interest has been shown in the hemagglutinins obtainable from plants. The study of them has been somewhat overshadowed by the more recently discovered serum agglutinins, which they so remarkably resemble in action. They have, however, played an important part in immunological research throughout its history. Ricin, the extremely toxic hemagglutinin from the castor bean (Ricinus communis) was used by Ehrlich (1897) in his first in vitro studies of the reactions between antigen and antib0dy.l The living organism was no longer to be regarded as an indispensable participant in the agglutinin-antiagglutinin reaction. Much remains to be done before the distribution of the hemagglutinins in the plant world can be estimated. From the observations made by Landsteiner and Raubitschek (1908), Mendel (1909), Eisler and Portheim (1909, 1926), Wienhaus (1909), and others, the substances appear to lack wide distribution.2 The early studies were confined to the toxic agglutinins: ricin, robin, cretin, and abrin. Later, non-toxic extracts were prepared in