Previous complement fixation studies of the serum of tuberculous patients and of infected and immunized rabbits using two antigens in parallel, one prepared from the S form and one from the R form of Mycobacterium tuberculosis, have led us to the opinion that S forms of the tubercle bacillus contain antigenic components which are lacking in R forms. The reaction of a small group of human cases to vaccination with B.C.G. lends some support to the view that antigenic deficiencies occur in the constitution of B.C.G.

Dr. R. S. Ferguson of the Saskatchewan Anti-Tuberculosis League kindly sent us the sera of 11 Indian children ranging in age from 9 to 16 years. These children had received 0.3 mgm. of B.C.G. vaccine intracutaneously (living culture prepared according to Calmette's method). Each developed a characteristic local infection of approximately the same intensity.

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