THERE is no uniformity of opinion concerning the fundamental biologic responses invoked in the human body when tubercle bacilli are introduced into it.
There is abundant evidence that an allergic response is set up in the tissues of experimental animals by the introduction of tubercle bacilli. The first dose of tubercle bacilli injected into the skin of a guinea pig does not cause hyperemia. After sensitization the same dose will cause hyperemia. Long1 has shown that a small dose of tubercle bacilli injected into the testis of a normal guinea pig has no immediate effect. However, if the animal has been previously sensitized, the same number of bacilli cause rapid degeneration of the testicle. It has been shown that leukocytes from normal animals are not harmed by contact with tuberculin, whereas leukocytes from tuberculous animals are damaged by similar contact.Aronson2 has shown that the growth of