TECHNIC FOR PREPARING BACTERIAL VACCINES 



213 



small cotton filter to remove larger clump of bacteria and particles of 

 agar, and is then placed in specially constructed centrifuge tubes (Inter- 

 national Centrifuge Company, see Fig. 63), covered with rubber caps, 

 and centrifugal ized for half an hour at a speed of approximately 2,800 

 revolutions a minute. The salt solution and bacteria above the 0.0^ 

 mark are then removed, and 5 c.c. saline solution is measured into the 

 tube, so as to make a 1 per cent, emulsion. If the sediment does not 

 reach the 0.05 mark, its volume is read on the scale, and a corresponding 

 quantity of saline is added to make the emulsion 1 per cent, in strength. 

 The bacteria are forced into suspension, the 

 vaccine transferred to a sterile tube, and the 

 microorganisms killed in the usual manner. 



Estimations of carefully counted suspensions 

 obtained by centrifugalization in the foregoing 

 manner gave the following results: 



5. Sterilizing the Vaccine and Testing its 

 Sterility. When, after the preliminary examina- 

 tion, the films for counting have been found satis- 

 factory, a pause is made to start the process of 

 sterilization, which may continue while the count 

 is being made. Either heat or a germicide may be 

 used for sterilizing vaccine, preferably the former. 



The vaccine may be placed in a test-tube, 

 which is then sealed (Fig. 64), and the whole im- 

 mersed in the water-bath; a simpler method, and 

 one just as good, is to place the flask or tube of 



vaccine in the bath, observing special care to see that the water is above 

 the level of the vaccine. 



Efficient sterilization is dependent upon permitting the process to con- 

 tinue at the minimum temperature for the minimum length of time. With 

 the water-bath at 56 to 60 C. sterilization is nearly always complete in 

 an hour. 



The vaccine should be now cultured to test its sterility. At least a 

 dozen platinum loopf uls are transferred, under strict aseptic precautions, 



FIG. 63. HOPKINS' 

 TUBE FOR STAND- 

 ARDIZING A BACTE- 

 RIAL VACCINE. 



