316 Microbes and You 



stroyed by heat) substance called complement, found in the 

 blood of warm-blooded animals, must also be present before dis- 

 solution of the cells can occur. If the antibody dissolves blood 

 cells, it is called hemolysin, and if it lyses bacteria, it is termed 

 BACTERiOLYSiN. The Wasscrmau test for syphilis employs hemo- 

 lysin as one step in this rather involved serological reaction. 



Antitoxins 



When sub-lethal doses of exotoxins are injected into animals, 

 the host responds by producing antitoxins which are capable of 

 neutralizing the specific toxins. Such an active immunity requires 

 a matter of days before the antitoxin titer builds up to levels which 

 are required to protect individuals from otherwise lethal doses of 

 toxin. If a person has been diagnosed as suffering from a disease 

 in which exotoxins are the destructive agents, a passive immunity 

 should be conferred on the patient bv injecting antitoxins produced 

 in other persons or in lower animals. The injected antitoxin will 

 neutralize the effects of the circulating poisons, and if the disease 

 has not progressed too far, this passive transfer of antibodies will 

 help to protect the patient until his own antitoxin-producing 

 mechanism can confer active immunity upon him. 



Neutralizing Antibodies 



When dealing with virus diseases, the antibody which reacts 

 with the pathogenic virus is capable of inhibiting the virus action, 

 and this antibody is termed a neutralizing antibody. The nature 

 of this reaction is not clear, but presumably it involves a physico- 

 chemical union of antibody molecules with virus particles. 



PREVENTIVE MEASURES IN DISEASE 



QUARANTINE 



The term quarontine has its origin in the French word quaran- 

 taine, meaning forty. As early as 1403 quarantine stations were 

 set up in Venice to control the spread of disease from passengers 



