ANTIBODIES AND OPSONINS. 103 



What is the theory of abstraction ? 

 What is meant by the retention theory? 

 What is the theory of Metchnikoff ? 

 What is Ehrlich's side-chain theory ? 



CHAPTER VIII. 



ANTIBODIES AND OPSONINS. 



ANTIBODIES. 



Alexins have already been mentioned in Chapter VII. 

 They are substances which can be destroyed by age or heat 

 (56 C.). On account of the latter property they are called 

 thermolabile. These substances (called complements by Ehr- 

 lich) have some bactericidal value of their own, and are 

 present in small quantities in normal serum. 



Antitoxins have been referred to. 



Bacteriolysins are antibodies formed in the blood of immune 

 animals, which have the power, under conditions, of dissolving 

 their specific bacteria. Their discovery and the elucidation 

 of their properties is due chiefly to Pfciffer. 



Agglutinins are substances in immune sera which were 

 worked out principally by Gruber and Widal. They have 

 the power, under certain conditions, of causing the bacteria 

 for which they are specific to clump. They will again be re- 

 ferred to under the heading of Typhoid Fever. 



Precipitins were added to the number of antibodies by 

 Kraus, who, by mixing with their specific sera filtrates of 

 bacterial cultures, was able to produce a precipitation. He 

 named the substances responsible for the reaction precipitins. 



The production of these antibodies is not unique with bac- 

 teria. A variety of substances have been shown capable of 

 antibody production. Red blood-cells will be mentioned as 

 an example. They are capable, after repeated injections, of 

 producing in the injected animals substances having the power 

 under proper conditions of dissolving similar corpuscles. 



