1. The thymus gland of young rats autotransplants easily when inserted in the muscles of the abdominal wall.

2. Destructive changes take place during the first 48 hours, when regenerative changes set in.

3. The regeneration is usually complete by the 14th day, when the new formed thymic lobules show differentiation into cortical and medullary zones.

4. The small thymic cells arise from the reticular epithelium in the regeneration of the transplant.