2O6 



CLINICAL BACTERIOLOGY AND H^MATOLOGY 



carbol thionin. In the case of tubercle bacilli it is best to fix 

 with saturated solution of perchloride of mercury (one or two 

 minutes), wash, stain in the ordinary way with hot carbol 

 fuchsin, decolorize for half to one minute in 2j per cent, sul- 

 phuric acid in methylated spirit, and to counterstain for about 

 five minutes in borax methylene blue, or in Delafield's 

 hsematoxylin. It is necessary to get the protoplasm of the 

 leucocytes clearly defined, so that a powerful stain is neces- 

 sary. Wash, dry, mount. 



Lastly, the films are examined with the oil-immersion lens. 

 The polynuclear leucocytes will be found to contain the bac- 

 teria, and it will be necessary to count the number in each of 

 fifty leucocytes in both your preparations i.e., in that made 

 with the patient's serum and in the control made with that 

 from a healthy person. The ratio between the two gives the 



FIG. 40. 



opsonic index. For example, in one case the number of 

 tubercle bacilli contained in fifty polynuclear leucocytes taken 

 at random amounted to 78. In the control specimen from a 

 healthy person the same number of polynuclears contained 

 172. The ratio i% = O'45 gives the opsonic index; it shows 

 that the patient has less than half the normal amount of 

 opsonin. 



The diagnostic value of the examination is considerable. 

 In acute infections the index is almost always low to the 

 organism causing the disease, but normal to others. For 

 example, in a case of severe furunculosis the index to 

 staphylococci was 0^65, and in a case of pustular acne 07. In 

 a case of septicaemia due to streptococci the index (tested 

 with a culture of streptococci obtained from the patient's 

 blood) was 0-6 on several occasions.. 



