298 INFECTION AND IMMUNITY. 



ognizable. Leucocytes are agglutinated by the 

 serum. A strong leucotoxic serum may be fatal 

 to the animal when injected into the peritoneal 

 cavity or blood stream, the exact cause of death 

 being obscure. 



oid ASC. Metchnikoff, taking the view that the phenom- 

 ena of old age depend on the destruction of vari- 

 ous tissue cells by the mononuclear leucocytes 

 (macrophages), expressed the hope that a lympho- 

 toxic serum might be utilized to combat the action 

 of these cells with the result that life would be 

 prolonged. Whether or not his view as to the 

 cause of old age is correct, his plan of antagonizing 

 it had to be abandoned because leucotoxic serums 

 do not injure the macrophages to the exclusion of 

 other leucocytes. 



Effect of The injection of a leucotoxic serum into the per- 



sernm U on t0 Re- itoneal cavity of a guinea-pig causes a temporary 



si stance of decrease in the number of leucocytes, and during 



Infections. ./ ? <=> 



this period of hypoleucocytosis the resistance of the 

 animal to peritoneal infections with the organisms 

 of typhoid and cholera is lowered. One may refer 

 this effect to the destructive action of the serum 

 on the leucocytes, by which phagocytosis is pre- 

 vented, or, according to Wassermann, it may de- 

 pend on the action of anticomplement which the 

 leucotoxic serum contains. (Leucocytes contain 

 complement, hence immunization with leucocytes 

 causes the formation of anticomplement.) It is 

 probable that both factors are of influence. In the 

 course of from twenty-four to forty-eight hours 

 after peritoneal injection of the serum, the leuco- 

 cytes reaccumulate to an enormous extent. Dur- 

 ing this secondary hyperleucocytosis resistance to 

 peritoneal cholera or typhoid is increased. Some 



