PATHOGENIC BACTERIA 261 



standardized against standard antitoxin. Dried standard 

 antitoxin is stable. 



The union between the toxin molecule and the antitoxin 

 molecule is a definite chemical combination. Antitoxin is 

 produced in the largest quantities in the spleen and bone 

 marrow of all susceptible animals. 



When a body is naturally infected by a pathogenic bac- 

 terium, or is immunized with living or dead pathogenic 

 bacteria which produce endotoxins, there is developed in the 

 blood serum and other body fluids of the infected animal a 

 variety of substances. As has been previously stated, the 

 body fluids contain no distinct antitoxins. The fluids con- 

 tain the following substances. 



Antibacterial Substances. These properties are mani- 

 fested by the ability of the blood serum and body fluids to 

 destroy the vitality of the bacteria without destruction of the 

 cell substance (bactericidal) , or to disintegrate in addition the 

 bacterial cell (bacteriolysis). Bacteriolytic action may be 

 due to autolysis of the bacteria themselves or to the direct 

 action of the serum. Two important molecular groups are 

 concerned in a bacteriolytic and bactericidal reaction. The 

 action of these chemical groups may be shown by the follow- 

 ing experiments. 



If an antibacterial serum, be it bactericidal or bacterio- 

 lytic, is heated to 60 C. for twenty minutes, then placed in 

 contact with the specific bacteria in vivo or in vitro, the bacteria 

 will not be affected. On the other hand, if some normal 



