GROWTH AND DEVELOPMENT OF SIX GENERATIONS OF ALBINO RATS UNDER TREATMENT WITH THYMOCRESCIN1

ALTHOUGH early workers on the thymus thought that it played a part in the control of growth and development, the work of Park and McClure (i) was – generally conceded to have demonstrated that extirpation of the thymus, in dogs, at least, led to no defects of either growth or development. This status of the thymus was abruptly changed in 1929 when a paper by Asher and Ratti (2) appeared. They found that rats fed McCollum's rachitogenic diet, kept in the dark and injected with aqueous thymus extracts grew, while the uninjected controls were stunted. A long and excellent series of papers by Asher and his coworkers followed and gave additional steps in the purification of the active substance. Asher (3) reviewed the work, which his group has carried on with thymus extracts, for Abderhalden's “Handbuch der biologischen Arbeitsmethoden.” He emphasized the growth and gonadotropic effects of the extract in dosages as low as 1 mg. daily and described in detail the method of extraction which yields this last and m...