27 



in combating streptococcus infections in man and in the lower animals. 



Hektoen and Ruediger* have shown that m-8 solutions of many salts 

 and other substances inhibit phagocytosis, presumably because these sub- 

 stances bind the opsonin. I have carried out a number of experiments 

 with rabbits for the purpose of determining whether or not intravenous 

 injections of weak solutions of antiseptics can prolong the animal's life 

 when inoculated with a fatal dose of streptococcus, but have found that 

 the animals thus treated invariably died earlier than the controls. We 

 must conclude, therefore, that great harm can be done by the indiscrimi- 

 nate use of drugs, or antiseptics, for the purpose of combating strepto- 

 coccus infections. The remedy used may act on the opsonin, for in- 

 stance, so as to hinder phagocytosis and thus do harm rather than good. 



Virulent streptococci are not freely, or scarcely at all, ingested by 

 normal leucocytes suspended in normal serum or blood, and hence these 

 organisms multiply in suspensions of leucocytes. Human leucocytes take 

 up virulent streptococci somewhat more freely than do the leucocytes 

 of rabbits and guinea-pigs. 



Rabbits can be successfully immunized with streptococci of mediunr 

 virulence, and this immunity is clearly dependent upon phagocytosis. 

 The immune rabbit serum has no streptococcidal power, but the leucocytes 

 suspended in the immune blood or serum readily take up and destroy 

 that strain of streptococcus which was used in the immunization. Other 

 strains of virulent streptococci are not taken up so readily by leucocytes 

 suspended in the immune serum. This is an important fact to be recog- 

 nized in the serum therapy of streptococcus infections. 



The action of the immune serum is not that of a stimulus for the leu- 

 cocytes but the effect is on the cocci. The immune serum has acquired 

 the power to change the cocci so that the leucocytes will ingest them, this 

 power being possessed only slightly by the normal serum. 



The opsonin of human serum is increased during the course of 

 a streptococcus infection, and according to Hektoen also after a subcuta- 

 neous injection of heated streptococci. 



The immune opsonin is more resistant to heat than normal opsonin. 



*Jonr. of Infect. Dis., 1905, II, 128. 



