XX 



THE OPSONIC INDEX 



DEFINITION OF OPSONINS AND THE OPSONIC INDEX— 

 TECHNIC OF DETERMINATION OF THE OPSONIC INDEX 

 —INTERPRETATION, VALUE AND LIMITATIONS OF THE 

 OPSONIC INDEX 



Denys and Leclef, Leisliman, Wright and Doug- 

 las and others have demonstrated that the real activity 

 of phagocytes depends upon a specific substance — 

 the exact chemical nature of which has been unde- 

 termined — existing in the serum of the blood. Irre- 

 spective of a certain amount of spontaneous phag- 

 ocytosis, which has been shown may take place, Sir 

 Almroth E. Wright, of St. Mary's Hospital, London, 

 has definitely proved that the subcutaneous injection 

 of dead bacteria is capable of the production of spe- 

 cific antibody, which taken up by the blood-serum 

 markedly augments the ability of the phagocyting 

 leucocytes to devour invading pathogenic bacteria. 

 To this specific substance, capable of preparing bac- 

 teria for ingestion, Wright assigned the name " opso- 

 nin," from the Greek verb bi^ovid, I prepare food 

 for. Opsonins, therefore, are those specific substances 

 or antibodies, not yet isolated, in the blood-serum, 

 possessed of the property to sensitize or prepare bac- 

 teria for phagocytosis. Opsonins are bacteriotropins 



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