Experimental Studies on Pneumococcus

The inefficiency of specific sera in the treatment of pneumonia must be attributed in part at least to the lack of exact knowledge of the nature of the infection and the processes whereby the human organism protects itself. To ascertain detailed facts regarding pneumococcus infection one must resort to laboratory animals, none of which so far as is known reacts to such infections in identically the same manner as does man. At the suggestion of Dr. Rufus Cole, to whom I am greatly indebted for much assistance and encouragement, I undertook the study of the immunity of the pigeon, but very early in the work it was found that to understand the reaction of the immune animal correctly it would be necessary to have exact knowledge of the reaction of the susceptible animal under identical conditions. A considerable part of this work was directed to the study of leucocytosis and phagocytosis, especially in their relations to virulence of pneumococci. One interesting theory of the nature of the crisis is based on phagocytosis in the lung (Tchistovitch) (I). Although Mennes (2) in I897 found that active immunity in rabbits to pneumococcus infection was due to a modification of the serum which allowed of phagocytosis, rather than to a specific change in the property of the leucocytes, Heim (3) in I9o8 observed that the bone-marrow of immunized rabbits had two and a half times as much protective power as did serum. Rosenow (4) in I9o6 claimed to have shown an increased resistance to heat and an increased phagocytic power of