PRODUCTION OF ANTIPNEUMOCOCCIC SERUM 587 



(1) When the mouse-protection test is applied by the technic de- 

 scribed in this paper, namely by carrying out the test in the zone in 

 which the law of multiple proportions is valid ; by controlling the dose 

 of culture by preliminary test against 0.5 unit of antibody; by using 

 mouse strains which have been shown to be uniform in their resistance 

 to pneumococci and by titrating the unknown serum or concentrate 

 against the protective power of 0.5 unit of antibody of a standard con- 

 trol serum, reliable and reproducible assays of the protective titer of 

 types I and II antipneumococcus serum can be made. 



(2) The in vivo method described in this report termed the "combin- 

 ing-equivalent method" which, in principle, measures the antibody 

 present by means of the amount of SSS with which it combines shows 

 a high degree of correlation with the mouse-protection test described in 

 the foregoing (in 62 samples r =■ 0.94 for type I and r = 0.91 for type 

 II antibody). 



(3) The use of the "combining equivalent technic" as an economical, 

 rapid, and reliable method for the titration of antipneumococcus serum 

 is suggested. 



(4) Standardization by several different methods in 1933 of the 

 United States National Institute of Health's standard serum Pll by 

 comparison with serum F146 gave the following results: Mouse-pro- 

 tection method, 300 type I units and 131 type II units per cc; by the 

 neutralization method, 333 type I and 150 type II units per cc; by the 

 combining equivalent method, 322 type I and 150 type II units per cc; 

 and by Heidelberger's method, 308 type I and 150 type II units per cc. 



(5) Standardization by three different methods in 1935 of three 

 sera — F146, Lyo Pll, and the British type I and type II dried stand- 

 ards, with proof of the deterioration of serum F146 as compared to se- 

 rum Pll, gave the following results for the antibody content of the 

 British standards as compared to serum Pll : Mouse-protection method, 

 1,150 type I units, 750 type II units; by the combining equivalent 

 method, 1,177 type I units, 720 type II units; by Heidelberger's 

 method, 949 type I and 426 type II units per cc of the respective 

 samples. 



Safety Tests 

 Antipneumococcic serum intended for therapeutic use must be 

 tested for the possible presence of harmful substances. The most 

 important tests are those planned to demonstrate freedom from 



