BACTERIAL POISONS. 167 



serum of animals by injecting these with several doses of sus- 

 pensions of cells. Hemolysin results from injecting an animal 

 with the red blood-cells from another animal, bacteriolysin 

 from the injection of bacteria. Hemolysins and bacteriolysins 

 are quite sharply specific. A rabbit injected with a suspension 

 of red corpuscles from the blood of a guinea-pig furnishes 

 hemolysin which destroys guinea-pig's red cells. A guinea- 

 pig injected into the peritoneal cavity with repeated small 

 doses of the cholera spirillum furnishes a peritoneal fluid con- 

 taining a bacteriolysin specific for the cholera spirillum. Still, 

 group lysins, like group agglutinins, are also found, for while 

 lysis takes place more promptly and in smaller amounts with 

 the cells of the same species of animal or with the same kind 

 of bacteria with which the animal furnishing the cytolytic 

 serum has been injected, it also occurs in a less marked degree 

 with cells from nearly related animals or with nearly similar 

 bacteria. 



Precipitins. — Precipitins are bodies which develop in the 

 serum of animals which have been given subcutaneous injections 

 of albuminous substances, and which, added to solutions of 

 the albumen with which the animals have been injected, cause 

 these to become cloudy and finally form a precipitate. In 

 other words, the serum of an animal injected with a serum 

 or other kinds of albumen causes precipitation in the homol- 

 ogous form of albumen. 



Thus, a rabbit may be immunized or adapted to hen's egg- 

 albumen. The rabbit's serum will then precipitate the hen's 

 egg-albumen. It may, however, imperfectly precipitate albu- 

 men from the egg of a species closely alhed to the hen. 



Again, a rabbit injected a few times at intervals of a day 

 or two with human blood-serum furnishes serum which even 

 in small quantities causes precipitation even in a weak solution 

 of human blood-serum, such as may be obtained from old 

 dried blood-spots. 



