ESTIMATION OF THE OPSONIC CONTENT OF THE BLOOD 211 



incubated for fifteen minutes at body temperature, which may either 

 be done in an ordinary incubator or in a special "opsonifier." 



After incubation the ends of the tubes are pinched off, drops are 

 mounted upon clean slides, and after having been well mixed by 

 passage up and down in the capillary pipette, exactly in the manner 

 in which the mixture was originally made, spreads on slides are 

 prepared by the aid of the narrow edge of a second slide, as in the 

 preparation of ordinary blood smears. After drying in the air the 

 specimens may be stained with aqueous methylene blue, with some 

 polychrome dye, such as Jenner's, Hastings', Wilson's, or Giemsa's 

 stain, or with Borrell's carbol-thionin, 1 the specimens being fixed 

 with absolute methyl alcohol, if aqueous stains are to be employed, 

 while this is, of course, unnecessary in the case of alcoholic mixtures. 

 Tubercle specimens are fixed by immersion for one minute in a 

 saturated aqueous solution of mercuric chloride. They are then 

 washed off in water, stained with steaming carbol fuchsin, washed with 

 water, decolorized in 2.5 per cent, sulphuric acid, treated with four 

 per cent, acetic acid solution to destroy the red cells, again washed 

 in water, counterstained with 1 per cent, aqueous methylene blue, 

 washed once more, and then allowed to dry. 



The average number of bacteria per leukocyte (phagocytic index) 

 is finally ascertained by going over at least a hundred cells, and the 

 opsonic index then calculated by dividing the patient's phagocytic 

 index by the normal, which is taken as unity. Example: Supposing 

 that with the patient's serum the average number of organisms per 

 cell was 5 and with the normal serum 10; then from the equation 

 10:1 : :5 \x, it would follow that the opsonic index is 0.5. 



When Wright's studies on the opsonins first appeared they 

 attracted an enormous amount of attention. This was largely owing 

 to the fact that the author attached a significance to his observations, 

 which, if justified, would have meant an enormous advance not 

 only in the diagnosis of certain bacterial infections, but also in their 

 treatment. I cite some of his more important diagnostic deductions: 



1 . Conclusions which can be arrived at when we have at disposal 

 the results of a series of measurements (opsonic determinations) : 



1 A saturated solution of thionin in distilled water is precipitated with a 10 

 per cent, soda solution; the precipitate is collected on a small filter, washed twice 

 with distilled water, and then dissolved in 5 per cent, carbolic acid solution 

 (1 gram : 100 c.c.). The solution must always be filtered before use. 



