A NTIB ODIES. 107 



pions. Briefly, opsonins are defined as substances occurring in 

 normal serum, and in a greater degree in immune serum, 

 which have the power of acting on bacteria or other sub- 

 stances and making them easier of assimilation by the phago- 

 cytes. Wright's technique for determining the power of the 

 opsonins on any given persons, or the opsonic index will be 

 given briefly. Necessary are 



1. Leucocytes (Phagocytes). These need not necessarily be 

 from the person to be tested. They are prepared by receiv- 

 ing a few drops of blood in some normal salt solution with 

 1 per cent, sodium citrate added. The mixture must be 

 shaken and centrifuged at moderate speed for five minutes. 

 The leucocytes will be found in a grayish layer at the top of 

 the sediment and may be pipetted off. 



2. Blood-serum from the person to be tested, obtained by 

 bleeding into glass capsules or tubes and centrifuging. 



3. Bacterial emulsion made from a young culture (twenty- 

 four hours) with 0.85 per cent, salt solution. Equal quan- 

 tities of these three factors are drawn up into a small capil- 

 lary tube, and mixed in a watch crystal and again drawn into 

 the tube. The tube is then sealed and incubated at blood 

 temperature (37.5 C.) for about twenty minutes. The mix- 

 ture is again shaken, and smears made and stained with any 

 good blood stain. Many of the bacteria will be found to 

 have been assimilated by the leucocytes. The contents of a 

 fair number, say one hundred, are counted and an average 

 made. Simultaneously with this test a control should have 

 been made, using the serum of a normal individual. The 

 results from the latter divided into the results of the person 

 being tested give the opsonic index e. g., if the normal one's 

 average is four bacteria per leucocyte and the tested one three 

 per leucocyte, we would have 3 -+ 4 = 0.75 ; 0.75 per cent, 

 would be the opsonic index for the tested person, or f the 

 quantity of normal, supposing normal to be 1. 



Wright has advocated the treatment of a great many dis- 

 eases with autogenous vaccines, using the production of op- 

 sonins as indicated by the opsonic index as a guide to the 

 time and the dosage of the vaccines. He recognizes a nega- 



