218 



BACTERIAL VACCINES 



to a slant of a suitable culture-medium, such as Loffler's blood-serum or 

 blood-agar; this is incubated at least twenty-four hours, or longer if the 

 organism is a slowly growing one. It is then examined, and if found 

 sterile, the preparation of the vaccine may be completed. If not, the 

 vaccine is heated for another hour, or, preferably, a new vaccine is 

 prepared. 



6. Diluting the Vaccine and Adding a Preservative. Having made 

 the count and sterilized the vaccine, it is next diluted with sterile saline 



solution so that each cubic centimeter 

 contains the dose decided upon. If 



FIG. 64A. A STOCK AMPULE OF 

 VACCINE. 



FIG. 64B. STOCK BOTTLE OF BACTERIAL 

 VACCINE. 



the treatment is likely to be prolonged, a sufficient number of doses 

 should be provided for. It is a good plan not to dilute all the vaccine, 

 but to preserve the remainder undiluted in case larger doses are subse- 

 quently needed. If, for instance, a vaccine of Staphylococcus aureus 

 contains 1,500,000,000 organisms per cubic centimeter and the dose 

 decided upon is 500,000,000 per cubic centimeter, sufficient vaccine for 

 30 doses is prepared by withdrawing 10 c.c. of vaccine in a sterile con- 

 tainer and adding 20 c.c. of sterile salt solution. This mixture is agitated, 



