[Thymus and bones].

Rat congenital osteopetrosis and cyclophosphamide (an immunosuppressive drug) induced osteocondensation are useful experimental models for the understanding of the relationships which seem to exist between thymus and bone. The high levels of seric alphafetoprotein found in the osteopetrotic tl rat raise the question of the persistance of embryonic characters in congenital osteopetrosis.