The presence of antibodies in the body fluids of the offspring of immunised parents has long been studied and variously explained. In 1912, Famulener2 published a clear summary of the work upon the subject up to that date. Renewed interest in the problem has been aroused by the work of the Department of Animal Pathology of the Rockefeller Institute for Medical Research, where the transmission of immunity to the Bacillus abortus is being studied. It has been shown by Little and Orcutt3 that agglutinins for this bacillus are transferred exclusively by the colostrum, since a calf from which colostrum is withheld does not show this agglutinin in its serum, although a high titre of agglutinin may be demonstrable in both serum and colostrum of the dam. Later Orcutt and Howe4, using a method of separating the protein fractions of serum devised by the latter5, 6, showed that the appearance of agglutinins in the serum of a calf fed with colostrum of high agglutinin titre was closely related to the appearance of euglobulin, which is absent from the blood of the newly born calf. Further, Smith and Little7 showed that this absorption of agglutinin from the digestive tract also occurred when the calf was fed with serum rich in that antibody. The association of agglutinin with the globulin fraction of serum, and in particular with the euglobulin fraction, has been demonstrated by Orcutt and Howe4, who found that “the agglutinins are associated with the protein fractions which are precipitated up to and including 16·4 per cent. of sodium sulphate,” and that “a large proportion of the agglutinins is associated with the fraction which is precipitated by 14·2 per cent. of sodium sulphate, euglobulin.” Again, although a milk might show a high titre of agglutinin, with no corresponding increase in the proportion of its globulin, yet the agglutinin was removed from the milk by a concentration of sodium sulphate which removed the globulin fraction of the protein.