Effects of thymic factors on growth of experimental tumors.

The effects of thymic factors on the growth of a chemically induced tumor have been studied. The thymic factors were obtained by a gentle isolation procedure which minimizes loss of material and biological activity. The administration of the thymic factors neither influenced the development or growth of the tumor nor the weight of the thymus or the spleen. A bigger thymus and a smaller spleen were observed in animals rejecting the tumor, whether or not they received the thymic factors.