i86 



PHAGOCYTOSIS OPSONINS AND BACTERIOTROPINS. 



treated with 4 per cent, acetic acid to dissolve the erythrocytes and counter- 

 stained with 1/2 per cent, of methylene blue in 1/2 per cent, of sodium car- 

 bonate. It is most important that tubercle films be carefully stained 

 because it is desirable to color every bacillus and yet not break up the 

 leucocytes (Fig. 27). 



With a i/ 1 2 inch oil immersion lens a minimum number of one hundred 

 polymorphonuclear leucocytes are now examined and the number of 

 microbes they contain enumerated. 



FIG. 27. Phagocytosis of tubercle bacilli. 



Similar calculation is undertaken with the normal control serum. The 

 fraction obtained by dividing the number of bacteria contained in 100 cells, 

 on the patient's slide, by the number in 100 cells, on the normal slide, gives 

 the opsonic index of the patient's serum. 



For example, the normal individual has 284 and the patient 262 bacteria 

 in 100 cells, the fraction which gives the patient's opsonic index would be 

 262/284 or 0.92. 



The principle of Wright's technique is simple, but it requires a great 

 deal of practice before it is mastered. Only then are the results reliable. 

 One must remember the same principles when counting the control slide as 

 when the patient's film is counted. If in the last case, for instance, the cocci 

 situated on the edges of the cells are not included in the count, the same 

 should also be excluded in the first case. The absolute count is of no 

 importance. It is the relative proportion which is significant. 



As a normal control, it is best to take the average of the phagocytic 



