Streptomycin, a recently developed antibiotic, figures prominently at the present time in the chemotherapy of tuberculosis in man. During the twentieth century the development of chemotherapy in tuberculosis in man has been pursued by two apparently divergent sets of investigators : first, those who believed in conservative progress based on thorough fundamental scientific study of possible therapeutic agents, translating elucidating laboratory and animal findings into human values; and second, those who were content to quickly transpose apparently encouraging in vitro and in vivo animal findings into human significance. The second group, of course, took encouragement from findings in diseases where only human studies were possible and from the fact that animal disease did not duplicate sufficiently that noted in man and therefore. did not permit the latter to be interpreted in the light of such scientific knowledge. Yet it is odd that the second group frequently justify their failures, both in interpreting human results and in supporting their contentions, on the basis of the results of animal tests.