230 APPLIED IlViMUNOLOGY 



we have the proportion of 900 : 1000 :: tr : 1, in which 

 00, the opsonic index, equals 0.9. 



Teclinic of Determination of the Opsonic Index. 

 — The technic of the opsonic index is a rather intricate 

 laboratory procedure, which, to be reliable or trust- 

 worthy at all, involves much practice in mastering the 

 details as stipulated by Wright. It demands that the 

 opsonist shall be a thorough bacteriologist as well as 

 an experienced laboratory worker. Briefly, the pro- 

 cedure may be described as follows: 



Material and apparatus required, 



(a) Pure culture of infective bacterium. 



(b) Specimen of serum of patient's blood. 



(c) Specimen of serum of normal or control 

 blood. 



(d) Normal washed leucocytes. 



(e) Centrifuge, preferably electric. 



(f) Thermostat or opsonizer. 



(g) Centrifuge or special test-tubes. 



(h) Teat and capillary pipettes, glass tubing, 

 slides, absolute alcohol, stains, etc. 



(i) Microscope. 



A few drops of the patient's blood and of the nor- 

 mal or control blood are collected in two glass tubes 

 drawn out on either end to capillary size (Fig. 22). 

 The straight or distal end, free of blood, is sealed in a 

 flame, and in a few minutes, after the tube cools, dur- 



