IMMUNITY 11 



phenomenon could also be observed if the bacteria 

 were injected into normal guinea-pigs, with a 

 sufficient quantity of cholera-immune serum. Other 

 workers also showed that this phenomenon would 

 also take place in vitro, as well as in the animal 

 body. The constituents of the blood serum which 

 gave rise to this destructive phenomenon are known 

 as " bacteriolysins." 



Soon after Pfeiffer's discovery Gruber and Durham 

 brought to light another specific property of immune 

 blood serum. These workers noticed that certain 

 bacteria when brought into contact with the serum 

 of an animal immunised against them were clumped 

 together, deprived of their mobility, and firmly 

 agglutinated. The substance which produced this 

 phenomenon they called " agglutinin." Later, Kraus 

 demonstrated the presence of yet another specific 

 antibody in immune serum. He showed that pre- 

 cipitates were formed when filtrates of cholera and 

 typhoid bacilU were mixed with their specific 

 immune sera. These substances he called '' pre- 

 cipitins." 



The treatment of the animal body, therefore, with 

 bacteria or their products gives rise to a variety of 

 reactions which result in the presence of the ** anti- 

 bodies " above described. Antitoxins, as we have 

 seen, can be produced by a variety of poisons, either 

 of animal or plant origin. Extensive investigations 

 have also shown, that, likewise, lysins, agglutinins, 

 and precipitins may be produced by the use of a 



