DETAILS OF METHOD OF OBTAINING THE OPSONIC INDEX 65 



7. Now place pipettes No. 1 (three healthy horses' serum mixture 

 the pool) and No. 2 (serum from sick horse) in the incubator for one- 

 half hour. 



8. Make a smear preparation from pipette No. 1 and also from 

 No. 2. Dry, fix, and stain. 



9. Count 200 leukocytes in specimen No. 1, and count how 

 many cocci have been taken up by phagocytosis in the 200 leukocytes. 



10. Do the same with No. 2. 



FIG. 29 



The smear, ready to be air-dried, fixed and stained. (Miller. 



The result, for example, may be as follows: 200 leukocytes in No. 1 

 have taken up 300 cocci (this is the mixture of the sera of three 

 normal horses); 200 leukocytes in No. 2 (sick horse's blood serum) 

 have taken up 150 cocci; therefore, taking the normal opsonic 

 index as 1 (one), the low opsonic index of the serum of the sick 

 horse is 0.5. 



When it is found that the opsonic index is low, vaccine treatment 

 (in our case the Staphylococcus pyogenes aureus vaccine) is indi- 

 cated. 



FIG. 30 



Wright's blood capsule filled with blood and ready to be centrifugalized for separating the 

 serum from the clot. (Miller.) 



In the above steps, to determine the opsonic index, small U-shaped 

 tubes, or, according to Wright, peculiar glass capsules are used for 

 collecting the blood sera. The mixing of the emulsion of leukocytes 

 of the sera and the bacterial emulsion is done in small pipettes. The 

 fluids are drawn up in equal amounts, first one, then a little air bubble, 

 then the second, and so forth. The three different fluids (serum, 

 5 



