VII. POTENCY TESTS 651 



purposes of the titration. Mice failing to show pneumococci in smears 

 of hearts' blood are regarded as neither deaths nor survivals, but as if 

 not injected. 



b. Culture. The culture of Type I Pneumococcus should be of such 

 virulence that it is fatal to mice in doses of 0.00,000,001 to 0.00,000,- 

 000,1 cc. (16 to 18-hour culture in steamed Witte peptone broth at a 

 pH of 7.5). At the beginning of each day's tests, mice are inoculated 

 intraperitoneal^ with 1 cc. of 0.00,000,000,1, 0.00,000,001, and 

 0.00,000,1 of the culture, two mice with each dose, to check the viru- 

 lence of the organisms. 



For the maintenance of virulence, cultures should be passaged 

 through the mouse monthly, being kept between passages in 50 per cent 

 defibrinated horse or rabbit blood broth (not incubated) in 1.0 cc. vials 

 in the ice-chest at 4°. When required for test, the cultures are incu- 

 bated and used as the inoculum for 5 cc. or 10 cc. tubes of Witte pep- 

 tone broth. A stock of Witte peptone broth which is known to be satis- 

 factory should be kept for the tests, and before it is expended another 

 supply should be prepared and tested in parallel with the stock before 

 being adopted for use. 



c. Serum. In every test a standard control serum should be avail- 

 able for purposes of comparison. Dilutions of this serum and of all se- 

 rums to be tested are made in 0.9 per cent saline solution, a different 

 pipette being used for each dilution. 



Author's Note: Parish recommends the use of 0.01 cc. of an 18-hour broth 

 culture rather than 0.001 cc. as the optimal dose for routine use. 



American Drug Manufacturers' Association 



The method was suggested by the Committee on Standardization of 

 Antipneumococcic Serum of the Biological Section of the American 

 Drug Manufacturers' Association, February 21, 1933, and revised De- 

 cember 29, 1933. 



a. Unit of serum. The unit of antipneumococcic serum shall be 1/200 

 cc. of F-146 or its equivalent which is 1/300 cc. for Type I and 1/150 

 cc. for Type II of P— 11. In the performance of the test, the dose of 

 serum used is the unitage tested for. In using the control serum P— 11 

 at a unitage of 300 units per cubic centimeter for Type I and 150 units 

 per cubic centimeter for Type II, which is the accepted potency of 

 this control serum, 0.5 cc. of a 1 : 150 dilution for Type I and of a 1 :75 

 dilution for Type II is injected. 



b. Test dose of culture. The test dose of culture is that amount of 

 culture which, when drawn up in the same syringe with a unit of con- 



