STUDIES ON THE SERUM OF VACCINATED ANIMALS. 13 



leucocytes, and from this fact we may assume that lactic acid is 

 endowed with properties that are antagonistic to those of bacterial 

 products ; in other words, one may attribute to it a negative chemio- 

 tactic power. 



Werigo does not agree with this interpretation. It seems to him 

 that lactic acid inhibits the attraction of leucocytes not by exercising 

 on them a truly repelling action, but by harming them or paralyzing 

 them, and so preventing them from feeling the attracting influence 

 of bacterial products. Nor does Werigo believe in the repelling 

 action of bacterial secretions any more than he does in the same 

 action on the part of lactic acid. In serious infections where no 

 phagocytosis is present the non-intervention of leucocytes seems 

 to him due not to the fact that they are repelled, but that they are 

 simply not attracted. In other words, there is an absence of posi- 

 tive chemiotaxis without any actual negative chemiotaxis. In 

 brief, "we find," says Werigo, " that a negative chemiotaxis for leu- 

 cocytes has not yet been proved in a satisfactory manner. The 

 question must be left to further experiments." 



Although Werigo's objections have some foundation, we believe 

 that a negative chemiotaxis of leucocytes does exist and that it may 

 be proved experimentally. 



Experiment 1. A normal guinea-pig was given an injection 

 in the peritoneal cavity of 1 c.c. of a two-day culture of strepto- 

 coccus. (The culture medium is a mixture of bouillon and serum 

 suitable for maintaining the virulence of the organism.) The 

 streptococcus employed was a very virulent organism kindly fur- 

 nished us by our friend Marmorek. 



Before injection the peritoneal cavity was found to contain a few 

 leucocytes largely of the mononuclear type and a few eosinophils ; 

 there were very few polynuclear microphages. 



After injection a small amount of exudate was removed at inter- 

 vals and stained preparations were made. 



Within a few minutes some organisms were found within mononu- 

 clear leucocytes. But as these leucocytes are few in number a 

 majority of the organisms remain free. 



After an hour the polynuclear leucocytes are to be found, but they 

 are still few in number; it is to be noted, however, that the majority 

 of them have taken up organisms. The number of these leucocytes 



