The Action of Hanson’s Thymus Extract on the Mouse Available to Purchase

In a recent paper Hanson (1934) described important results as to the effect of extracts of the thymus gland on growth and morphological differentiation. In his experiments, albino rats from an inbred strain were daily injected during a long period with a thymic extract, the preparation of which is fully described by him in a previous paper (1930). Four successive generations were bred, the young being treated from the 16th day, and the treatment continuously applied even during pregnancy. Comparison with the controls shows a striking acceleration of growth, quite conspicuous from the growth curves, an earlier appearance of such morphological changes as the growth of the hair and the teeth, the opening of the eyes and the ears, and an earlier sexual maturation, as manifested by the external descent of the testes and the opening of the vagina. The injections have a cumulative effect, the results being most striking in the F₂ animals, with a slight increase of effect through the following generations. The average time for the opening of the vagina may be reduced, from the 60th to 70th day in the controls, to the 18th to 19th day in F₄, the appearance of the hair from the 14th to 17th day to the 3rd day.