282 The Phagocytic Power of the Blood 



blue, or perhaps better with gentian violet and counter- 

 stained with Bismarck brown or vesuvin. 



The final step in the process is the enumeration of the 

 bacteria in the corpuscles by averaging the number taken 

 up by the cells. Only typical polymorphonuclear cells 

 should be selected for staphylococcic cases, and separate 

 averages made for polymorphonuclear and mononuclear 

 cells in tubercle bacillus cases. It is best to follow cer- 

 tain routine methods of enumeration. Some who content 

 themselves with a count of the number of bacteria in 20 cells, 

 secure less accurate results than those who count 50 cells. 

 It is usually best to count one-third of the cells in the central 

 portion of the spread, one-third at the edge, and one-third 

 at the end. In each portion no other selection of cells should 

 be made than the elimination of other than polymorpho- 

 nuclear cells and the elimination of all crushed or injured 

 cells ; the others should be taken one after the other, as they 

 are brought into the field with the mechanical stage. After 

 the bacteria included in each of the accepted number of 

 cells selected as the standard has been enumerated, an 

 average is struck. 



The "opsonic index" is determined by dividing the 

 average number in the patient's serum preparation by the 

 average in the normal serum preparation. 



Irishman's* studies of the phagocytic power of the blood 

 show that in cases of furunculosis, etc., with each recru- 

 descence of boils, there is a marked diminution of the pha- 

 gocytic power of the blood, and with each improvement, 

 a marked increase. 



McFarland and 1'Englet found by an examination of the 

 blood of 24 supposedly healthy students and laboratory 

 workers that it was possible to prejudge, by the phagocytic 

 activity of the cells, the past occurrence of suppuration and 

 present liability to it. 



Wright and Douglas use the opsonic index as a guide to 

 the specific therapy of the infectious diseases. If the 

 opsonic index is low they believe bacterio-vaccination is 

 indicated. In its administration, however, care must be 

 taken to administer a counted number of bacteria, and to 

 make frequent opsonic estimations to determine the good 

 or ill effects accomplished. Thus, the administration is 



* "Lancet," 1902, I, p. 73. 

 f "Medicine," April, 1906. 



