[Study of the thymus as a source of humoral factors stimulating antibody formation].

A fraction stimulating antibody formation in neonatal animals was obtained in separation of the calf thymus extract (1A) prepared by the method of Goldstein et al. on a column with Sephadex G-25 (fine). Testing of the activity of analogous fractions of the extracts of calf tonsils, spleen, lymph nodes and the liver led to a supposition that the thymus was the only source of specific humoral factor stimulating antibody formation, which could accumulate in the peripheral lymphoid formations. Low activity of tonsillar extracts failed to confirm the hypothesis on the role played by the tonsils as the central immunity organ similar to the bursa Fabricii.