214 A MANUAL OF BACTERIOLOGY 



Method of Determining the Opsonic Index 



The requisites are : 



1. Several Wright's pipettes with india-rubber teats. 



2. The serum of the patient to be tested. 



3. The serum of a healthy person for a control. 



4. A suspension of the organism for which the deter- 

 mination is to be made. 



5. A suspension of living leucocytes. 



1. Wright's pipettes with india-rubber teats. These are 

 made of glass tubing of the form shown in a, Fig. 35, 

 which is about two- thirds full size. Glass tubing must be 

 chosen which properly fits the teats. A piece of glass- 

 tubing about 4 inches in length is taken, heated in the 

 blowpipe flame until quite soft, then it is taken out of 

 the flame and the two ends are drawn steadily apart ; 

 the more they are drawn apart, the finer will be the bore 

 of the tube about ^ in. is a suitable size. The middle 

 of the capillary part should then be introduced into a 

 small white gas- flame and drawn apart so as to form 

 two pipettes. By filing off the sealed end at a suitable 

 spot the open extremity may be slightly contracted as 

 shown in b ; this prevents the column of fluid in the tube 

 moving so quickly. 



2 and 3. The sera. These two specimens should be 

 taken at about the same time, and the determination 

 should be made as soon as possible. 



The blood is preferably collected in a Wright's capsule 

 (Fig. 35, d). Both ends of the pipette are broken off, 

 and the blood is collected by immersing the bent end in 

 the blcod as it luns from a prick with a Hagedorn or 

 triangular needle in the ear or finger. The capsule, which 

 should be at least one-third filled, is then sealed in the 

 flame, the dry or straight end being sealed first. After 



