OPSONIC TECHNIC 89 



solution added and again the mixture centrifuged, the fluid 

 removed, leaving the leukocytes and red cells, which is known 

 as the leukocyte emulsion or "washed leukocytes" 



Third, Preparation of the Serums. Small capsules made from 

 glass tubing (see Fig. 47) are used to obtain the blood from a 

 normal or healthy person; the blood by attraction is made 

 to fill a capsule, the end is sealed with wax, and the corpuscles 

 separated by the centrifuge. A capsule with blood from an 

 infected person is obtained, and the serum separated in the 

 same way. 



Fourth, Mixture of the Emulsion, the Leukocytes, and the 

 Serum. This is performed by drawing into a pipet similar 

 portions of the emulsion, the leukocytes, and the serum, mixing 



Fig. 47. Wright's blood-capsule. Illustration shows technic of filling same. 



a drop of each on a slide. The mixture is then drawn up again 

 into the tube, the end of which is now sealed and the tube placed 

 in an incubator at 37 C. for fifteen minutes. The end is 

 broken, and a drop of the mixture is distributed evenly on a 

 glass slide and stained. The same procedure is carried on 

 with the serum of the infected person, but using the normal 

 leukocytes. 



Under the microscope the number of bacteria in the proto- 

 plasm of at least fifty polynuclear cells are counted (see 

 Fig. 46) in the mixture with the normal serum and in the 

 mixture with the infected serum, and an average for each 

 obtained; the proportion that the diseased bears to the normal 

 is the opsonic index. 



