II. CYTOTOXINS 



Cytotoxins Definition Leucotoxin Nature of 

 the Cytotoxin Anticytotoxin. - - After it had been 

 found that the injection of an animal with red blood 

 cells of another animal was followed by the produc- 

 tion of definite, specific reaction substances, investi- 

 gators experimented to see whether this was also 

 the case if other animal cells were used. Injections 

 were made with white blood cells, spermatozoa of 

 other animals, etc., and there resulted a series of 

 reaction substances, entirely analogous to the 

 haemolysins, which were specific for the cells used for 

 injection. These sera Metchnikoff calls cytotoxins. 

 After Delezenne had published a short article on a 

 serum haemolytic for white blood cells, Metchnikoff 

 undertook a study of the substances produced in 

 sera of animals treated with leucocytes of another 

 species. He injected guinea pigs with the mesen- 

 teric glands and bone marrow of a rabbit. He 

 also injected for several weeks half an Aselli's pan- 

 creas at a time, at intervals of four days. If he 

 withdrew serum from such a guinea pig he found 

 this to be intensely solvent for white blood cells of 

 a rabbit. He called this serum leucotoxin. This 

 leucotoxin is very poisonous for these animals, and 



