Family and biologic variables in the same etiologic studies of schizophrenia: a proposal.

• First, he systematically identified methyleneblue-stained rod-shaped bacteria in tuberculous lesions from diseased organs of men and animals, ruling out the hypothesis that different forms of the disease might be caused by different agents. • Second, he carefully prepared pure cultures of the bacillus, separating them from any other noxious agent that might have been present in the diseased tissue. • Third, he inoculated these cultures into a variety of animals, producing unmistakable tuberculous lesions from which he could again extract the bacillus; comparable animals who were not inoculated remained healthy.