76 CLINICAL BACTERIOLOGY 



We therefore must extract from the stock vaccine bottle 

 diluent solution to the quantity of 7*81 c.c, to make room 

 for the like quantity of bacterial emulsion, which has been 

 previously drawn up by the syringe to be injected later into 

 the stock vaccine bottle by passing the needle through the 

 rubber cap, giving us a standardized dose of vaccine of 

 1,000,000,000 bacteria in every cubic centimetre of solution. 

 Having now obtained this strength, we can give what 

 quantity we desire — i.e., a ^ c.c. containing 500 million; 

 in 1 c.c, 1,000 million; and so on. 



As soon as we have made an emulsion and obtained the 

 exact ratio of bacteria, we place the tube in a moist steri- 

 lizer, to kill all bacteria, at a temperature of 58° to 60° C. 

 for forty-five minutes. Care must be taken not to overcook, 

 as the therapeutic value of the vaccine is reduced thereby. 

 On the contrary, it is essential to kill all bacteria, and to prove 

 this a small quantity should be pipetted into a culture-tube 

 and incubated. If no growth takes place in from twenty- 

 four to forty-eight hours, one may take it the emulsion 

 is sterile. The stock bottle into which the vaccine is to be 

 placed is filled with (after sterilization) a -?r per cent. 

 carbolic acid and 0*85 per cent, salt solution, and sterile 

 rubber caps applied, and as already explained, an exact 

 quantity of this solution has to be withdrawn from the 

 bottle by a syringe, the needle of which is passed through 

 the rubber caps, to make room for the same quantity of 

 emulsion, which is also injected through the cap with the 

 syringe. To make sure of absolute sterility, the needle 

 should be passed through a drop of lysol put on the cap 

 each time it is punctured. 



