ESTIMATION OF THE OPSONIC CONTENT OF THE BLOOD 225 



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 Bon-ell'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 

 4 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 a great 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): 



(a) When a series of measurements of the opsonic power of the 

 blood reveals a persistingly low opsonic power with respect to the 

 tubercle bacillus, it may be inferred, in the cases in which there is 

 evidence of a localized bacterial infection which suggests tuber- 

 culosis, that the infection in question is tuberculous in character. 



(6) When repeated examination reveals a persistently normal 

 opsonic power with respect to the tubercle bacillus, the diagnosis 

 of tubercles may with probability be excluded. 



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. 

 15 



