Fowl antibody: II. The composition of specific precipitates formed by antisera to serum albumin, haemoglobin and myoglobin and some properties of non-precipitating antibody.

Specific precipitates formed in 0.9 per cent and 8 per cent NaCl and the precipitates formed by raising the salt concentration of `0.9 per cent' supernatants to 8 per cent were measured quantitatively. With antisera to haemoglobin and myoglobin the antigen in the precipitates was also measured. Except for some very high antibody/antigen ratios found in some cases in antibody excess, these ratios were the same as those found with rabbit antibody, and did not depend on salt concentration. Non-precipitating antibody, prepared by serial absorption of antiserum with small portions of antigen, did not precipitate with antigen even in 8 per cent NaCl; it co-precipitated with homologous rabbit antiserum and delayed its flocculation, but produced no permanent inhibition. Rabbit antiserum to washed specific precipitates made from fowl antisera was used to confirm the presence of two globulins, one a macroglobulin, in the precipitates, and to study their different properties when free in whole serum and when combined with antigen.