VIII. STERILITY TESTS 663 



broth to dilute the preservative so that its concentration shall not exceed 

 0.01 per cent, but not more than 5 cc. need be planted from any con- 

 tainer. In case contaminations appear in any of the tubes planted, the 

 test may be repeated with the same number of containers but no lot 

 shall be passed until the final test shows no growth throughout, and a 

 lot shall be discarded if the same organism appears in more than one 

 test. 



IX. Preparation of Diagnostic Antipneumococcic Rabbit Serum 

 Massachusetts Antitoxin and Vaccine Laboratory Method 



a. Vaccine. Eighteen hour broth cultures of highly virulent, type- 

 specific pneumococci are centrifuged, the sediment taken up in physio- 

 logical salt solution in quantities to give a corrected Gates reading of 

 2.0, and the suspension heated for 15 minutes at 100°. This results in a 

 suspension containing approximately 25 billion organisms per cubic 

 centimeter and is used as a stock supply of vaccine. No preservative is 

 added. For the injection of rabbits, the stock vaccine is diluted 1 to 10 

 with physiological saline solution, thus giving a suspension containing 

 about 2.5 billion organisms per cubic centimeter. 



b. Injection of rabbits. A minimal number of six rabbits should be 

 maintained on each type of vaccine. All injections are given intrave- 

 nously, the schedule and dosages following the scheme given below : 



Week Monday Tuesday Wednesday Thursday Friday Saturday 

 0.2 0.5 



0.2 0.5 1.0 



1.0 2.0 



1.0 2.0 3.0 



2.0 3.0 



1.0 2.0 3.0 



BLEED 

 2.0 3.0 



1.0 2.0 3.0 



BLEED 



c. Bleeding of rabbits. The rabbits are bled by cardiac puncture 

 every three weeks after routine bleedings are initiated and, with care- 

 ful handling, the animals may be kept for an average of at least a year. 



