The importance of mixed infection in tuberculosis is at present a much-disputed question. Some investigators believe that secondary invasion by pyogenic organisms is responsible for practically all the damage done in "consumption," while others believe that the tubercle bacillus alone is capable of producing all the pathological changes. Between these two extremes of opinion are found those occupying all possible positions in the middle ground. The reason for this great disagreement of opinion among investigators and clinicians is the inefficiency of the methods used in the diagnosis of mixed infection. Practically all of our data on the subject, up to the present time, have been obtained by: (1) animal experimentation; (2) post-mortem histological and bacteriological examination of the lung; (3) blood cultures before and after death; and (4) sputum examination.
The results obtained in animal experimentation are greatly at variance with each other. Sputum inoculated into rabbits and