HISTORIC DEVELOPMENT OF IMMUNOLOGY 37 



Bordet and Biltz consider the combination not 

 as a true chemical union, but as being of the na- 

 ture of an absorption phenomenon. More re- 

 cently, Abderhalden and others have, by the use 

 of polariscopic methods, demonstrated a true 

 disintegration of some toxic substances by im- 

 mune sera. 



Opsonins - - In 1903 Wright and Douglas 

 pointed out that there are certain substances in 

 sera which so affect bacteria that they are more 

 easily taken up and disposed of by the leuko- 

 cytes. These substances they termed "opso- 

 nins." Wright and Douglas decided that the 

 amount of opsonins in sera is variable; that 

 these substances are of importance in infection, 

 and can be increased or decreased by injection 

 of killed cultures of bacteria. They express the 

 amount of opsonins present in serum in terms 

 of the phagocytic index of the patient's blood to 

 the phagocytic index of serum from normal in- 

 dividuals. 



