308 INFECTION AND RESISTANCE 



From the discovery of antibacterial properties in the extracts of 

 leukocytes it is but a logical step to the attempt to utilize these sub- 

 stances therapeutically. This was especially called for in view of 

 the disappointing results which have attended the injection of even 

 large amounts of bactericidal sera into animals and human beings in 

 whom anthrax bacilli, streptococci, or any other of the invasive bac- 

 teria or true parasites had gained a foothold. Petterson 48 was 

 probably the first to study this phase of the problem systematically 

 in connection with anthrax infection in dogs and rabbits. In pre- 

 liminary studies he claimed to have determined that when leukocytes 

 are left in contact with serum for four hours or longer there develops 

 in the mixture a bactericidal power far superior to that which is 

 possessed by these elements when separately kept in salt solution and 

 mixed only just before the bactericidal tests. He attributes this to 

 the fact that in dogs, at least, the leukocytes furnish bactericidal 

 substances to the serum an assumption which is entirely in accord 

 with the earlier opinion of Denys and Kaisin, 49 which we have men- 

 tioned in another place. In direct continuance of these experiments 

 he injected leukocytes into dogs at the same time at which he in- 

 fected them with anthrax and observed a moderately protective in- 

 fluence, which, however, he admits was not very great. He followed 

 this work in 1906 with similar observations on the protective influ- 

 ence of leukocytes in intraperitoneal infections of guinea pigs with 

 typhoid bacilli. In these experiments 50 he made the curious ob- 

 servation that, although such protective influence was unquestionable, 

 the guinea pig leukocytes contained no bactericidal substances active 

 against typhoid bacilli. In consequence he concluded that the de- 

 struction of these bacteria in the guinea pig was due entirely to the 

 serum-antibodies absorbed by the micro-organisms before phago- 

 cytosis, even when the actual destructive process took place intra- 

 cellularly. The protective effect following on the injection of the 

 leukocytes he attributed to an indirect influence of the leukocytic 

 substances in stimulating the more rapid accumulation of alexin or 

 complement in the peritoneum, with consequently more powerful 

 phagocytosis. Following this, in 1908, Opie 51 carried out experi- 

 ments in which he observed that leukocytes injected intrapleurally 

 into dogs, together with tubercle bacilli, exerted a distinct protection 

 in that the course of the disease was prolonged and the tendency 

 toward healing was more pronounced than in the controls. 



In the same year extensive observations on the protective prop- 

 erties of leukocyte extracts were published by Hiss. 



48 Petterson. Centralbl. f. Bakt., Vol. 36. 1904. 



49 Denys and Kaisin. "La Cellule," Vol.' 9, 1893. 



50 Petterson. Centralbl f. Bakt.., Vols. 40 and 42, 1906. 



51 Opie. Jour. Exp. Med., 1908. 



