214 



BACTERIAL VACCINES 



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

 complished by counting the bacterial elements con- 

 .g 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. 



g 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 



3 1 vaccine to be examined should be secured before 



| - sterilization is undertaken. 



pq -3 The counting or standardization may be done 



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

 normal blood and bacterial emulsion and counting 



g g\ the proportion of corpuscles to bacteria in our mix- 



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



,| & with the hemo cytometer, as in the enumeration 

 H ^ 2 of red blood-corpuscles; (c) for standardizing large 



^jU & g, quantities of bacterial vaccine the method of Kolle 

 . tj 10 (x g or (d) that of Hopkins may be used. 

 * 5 "5 (0 Method of Wright. Prepare a simple capil- 



S ; lary pipet, making a mark on its stem about an 



* fe 



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



<(j C^ 



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

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



"g g .g one volume of sodium citrate solution, one of blood 

 j ^ g and then either one volume of bacterial suspension 



*N tja 



I or two or more volumes, if it appears on inspection 

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



b m 



g to the cubic centimeter. To guard against crimping 

 | of the corpuscles in drying the films, Wright advo- 



! | "f cates aspirating one or two volumes of distilled water 

 ^ ^ after the blood and bacterial suspension, 

 fl? |3 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 



