REACTION OF THE HOST TO INFECTION 213 



Cytolysins. Pfeiffer (1896) found that guinea-pigs, when 

 injected repeatedly with non-fatal doses of cholera germs, reacted 

 to this treatment by producing a something which would dissolve 

 these bacteria. This new property was present in the blood and 

 also in the peritoneal fluid. The substance was called bacterioly- 

 sin. Subsequent investigators have shown that bacteriolysins 

 can be produced for a great variety of micro-organisms, although 

 in none can the reaction be better demonstrated than in the 

 cholera vibrio originally employed by Pfeiffer. Lysins, or 

 dissolving substances, have been produced for very many other 

 kinds of cells also, of which those for red blood cells (hemolysins) 

 are perhaps the most important. It seems to be possible to 

 produce a lysin (cytolysin) for any kind of cells by injecting these 

 cells into an appropriate animal. 



Cytolysins, including bacteriolysins, are active only when 

 comparatively fresh. Upon standing for a day at room tem- 

 perature, or upon heating to 56 C. for 30 minutes, the cytolytic 

 power disappears. This power is, however, restored in a re- 

 markable manner if the cytolysin and the cells to be dissolved are 

 injected together into a normal animal, for example into the 

 peritoneal cavity of a guinea-pig, or if a fresh normal blood serum 

 be added to the mixture in the test-tube. The experiment results 

 as follows: 



Immune serum + cholera germs = Bacteriolysis. 



Immune serum (old or heated) -f cholera germs = No bacteriolysis. 

 Normal serum + cholera germs = No bacteriolysis. 



Immune serum (old or heated) -(- normal serum + cholera germs 



= Bacteriolysis. 



This experiment proves that the cytolytic property of the serum 

 depends upon the presence of at least two recognizably different 

 substances, one of which is present in fresh normal serum and 

 in fresh immune serum but is destroyed on standing or by heating, 

 and a second which is present in the immune serum and which 

 is not destroyed so readily. 



