STUDIES ON THE MECHANISM OF IMMUNITY IN TUBERCULOSIS : THE ROLE OF EXTRACELLULAR FACTORS AND LOCAL IMMUNITY IN THE FIXATION AND INHIBITION OF GROWTH OF TUBERCLE BACILLI.

1. The fate of bacilli of reinfection at the portal of entry and in metastatic foci, and also the associated host responses, are essentially similar in rabbits and guinea pigs. 2. However, in the guinea pig tubercle bacilli of reinfection are more effectively fixed at the portal of entry than in the rabbit. 3. The guinea pig fixes at the site of reinfection unrelated substances, such as trypan blue and agar particles, more effectively than the rabbit. 4. At the site of a local non-specific inflammation precipitins from the circulating blood accumulate in higher concentration in tuberculous guinea pigs than in tuberculous rabbits. 5. These differing fixing capacities of the two species are associated with differences of extracellular character in the inflammation resulting from reinfection. (a) In the guinea pig, whose tissues are highly sensitized and greatly injured by the tubercle bacillus, the lymphatics adjoining the site of reinfection become thrombosed. In the rabbit whose tissues are moderately sensitized and less injured by the tubercle bacillus the corresponding lymphatics remain open. (b) In the guinea pig the fibrinous network at the site of inflammation forms a fine sieve-like structure. In the rabbit this network forms a coarse sieve-like barrier. 6. In rabbits and guinea pigs primarily infected, the destruction of tubercle bacilli takes place first and most extensively at the portal of entry. At this time they are less effectively destroyed in the nearest metastatic foci. Simultaneously they are still growing without hinderance in such foci in remote internal organs. 7. The cell-free body fluids of normal animals support the growth of tubercle bacilli in vivo. The body fluids of tuberculous animals under the same conditions are bacteriostatic for this microorganism. 8. Tubercle bacilli often multiply by preliminary subdivision into non-acid-fast granules, from which the acid-fast rods sprout. This confirms the work of Kahn.