120 IMMUNE SERA 



kills them within a few hours. Non-fatal doses at 

 first excite a marked hypoleucocytosis, which is 

 followed after a few days by a compensatory hyper- 

 leucocytosis. Leucotoxin destroys the mononu- 

 clear as well as the polynuclear leucocytes of the 

 animal, as was shown by Funk. Leucotoxin which 

 had been derived by injection of the leucocytes of 

 horses, oxen, sheep, goats, or dogs acted only on 

 the leucocytes of that species, not on the leucocytes 

 of man. So far as the mechanism of the cytotoxic 

 action is concerned, it has been found that this is 

 the same as that of the haemolysins. The action of 

 the specific cytotoxic serum is always due to the 

 combined action of two substances in the serum, a 

 specific immune body, and an alexin or comple- 

 ment present also in normal serum. The cyto- 

 toxic sera, like the hsemolytic sera, are rendered 

 inactive by heating to 55 C. In other respects 

 also the cytotoxic sera maintain the analogy to 

 the hasmolytic sera. Thus it is possible by immu- 

 nizing with a cytotoxin to obtain an anticytotoxin. 

 Metchnikoff, for example, was able to produce an 

 antileucotoxin by injecting animals with leuco- 

 toxin. This antibody inhibited the action of the 

 leucotoxin. 



Neurotoxin. Delezenne and Madame Metchni- 

 koff have injected animals with central-nervous- 

 system substance, and so produced a specific neuro- 

 toxin. They injected ducks intraperitoneally, giving 



