134 BACTERIOLOGY FOR NURSES 



free from serum are added to a suspension of bacteria which have 

 not previously been sensitized by opsonins practically no phagocy- 

 tosis occurs. 



A method has been devised whereby the relative amount of 

 opsonins present in the blood of a sick person and a normal healthy 

 person may be estimated. For the procedure it is necessary 

 to have (1) blood serum from the patient and also from a healthy 

 person, (2) washed leukocytes, and (3) a suspension of the organ- 

 isms the opsonin for which is to be measured. 



Serum is obtained from the patient by pricking the finger or 

 ear lobe and allowing the blood to flow into a Wright's capillary 

 tube (Fig. 22). The tube is easily made by bending in a flame 

 glass tubing with a small lumen. After the 

 clot has formed the tube can be broken and 



FIG. 22. A, Wright's Capillary Tube for collecting Blood ; B, Wright's 

 Capillary Pipette used for Opsonic Index. 



the serum withdrawn. Serum is obtained from a normal indi- 

 vidual in the same manner. 



An emulsion of leukocytes is prepared by dropping about twenty 

 drops of blood from a pricked finger into 20 c.c. of normal saline. 

 The mixture is centrifuged until the leukocytes appear as a layer 

 of cream over the red corpuscles. The clear upper fluid is removed 

 by means of a pipette and the upper layer of the sediment added 

 to 10 c.c. of normal saline. This second mixture is centrifuged, 

 after which the clear upper fluid is discarded and the remaining 

 leukocytic emulsion used for the test. The purpose of this prepara- 

 tion is to wash the leukocytes free from influencing substances 

 that might be present in the blood from which they were taken, 

 and also to obtain a greater number of leukocytes in a small quan- 

 tity of emulsion than would be found in the same amount of whole 

 blood. 



The bacterial suspension is prepared by gently rubbing a loopful 

 of the growth of the organism taken from an agar culture into 



