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BACTERIAL VACCINES 





II 



4. Counting of the Bacterial Suspension. Standardization, best ac- 

 complished by counting the bacterial elements con- 

 tained in a unit volume of the suspension, is necessary 

 in order to adjust our initial dose as experience will 

 dictate and for guidance in making subsequent in- 

 jections. 



In dealing with a vaccine we have to count both 

 the dead and the living bacteria, making no dis- 

 tinction, for both furnish the chemical agent that 

 calls forth the elaboration of bacteriotropic sub- 

 stances. Inasmuch as sharp definition and the 

 staining properties of bacteria may be lost in the 

 process of sterilization by heat, the specimen of 

 vaccine to be examined should be secured before 

 sterilization is undertaken. 



The counting or standardization may be done 

 in several ways: (a) By mixing equal portions of 

 normal blood and bacterial emulsion and counting 

 the proportion of corpuscles to bacteria in our mix- 

 ture (Wright) ; (6) by diluting, staining, and counting 

 with the hemo cytometer, as in the enumeration 

 of red blood-corpuscles; (c) for standardizing large 

 quantities of bacterial vaccine the method of Kolle 

 or (d) that of Hopkins may be used. 



(a) Method of Wright. Prepare a simple capil- 

 lary pipet, making a mark on its stem about an 

 inch from the tip, and fit a teat to its barrel (Fig. 

 59). Cleanse and prick the finger, press out a drop 

 of blood, take up the pipet and draw up into it first 

 one volume of sodium citrate solution, one of blood 

 and then either one volume of bacterial suspension 

 or two or more volumes, if it appears on inspection 

 to contain much fewer than 500,000,000 of bacteria 

 to the cubic centimeter. To guard against crimping 

 of the corpuscles in drying the films, Wright advo- 

 cates aspirating one or two volumes of distilled water 

 after the blood and bacterial suspension. 



Now expel from the pipet first only the distilled 

 water and bacterial emulsion, and mix these, so that 

 there may be no danger of the red corpuscles becoming hemolyzed, and 



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