378 BIOLOGY OF PNEUMOCOCCUS 



serums and found the indices to vary as did the number of pro- 

 tective units. The ratio of the precipitin index to protective units 

 in monovalent serums was between 2.8 and 4.8 for Type I and 

 about ten times greater for Type III. Lower values prevailed in 

 polyvalent antipneumococcic horse serum and in mixtures of 

 heterologous monovalent serums. A relative increase in precipitin 

 activity was found in the refined and concentrated serums tested. 



The experiments of Avery and Goebel (1931 ) 45 with the arti- 

 ficially conjugated Type III capsular polysaccharide-horse serum 

 globulin would seem to argue for the unity of type-specific pre- 

 cipitins, agglutinins, and protective antibodies. 



In a systematic study of the quantitative relations existing be- 

 tween the various specific antibodies in Type I and II antipneu- 

 mococcic horse serum, Felton (1931) 407 determined for Type I 

 Pneumococcus the correlation coefficient between protective and 

 precipitin titer as 0.93 ; between protection and agglutination the 

 figure was 0.80 ; between protection and neutralization it was 

 0.88 ; and between protection and the amount of protein precipi- 

 tated with specific carbohydrate it was 0.91. From this degree of 

 correlation it appeared to Felton that, at least for freshly drawn 

 horse serum, the precipitin test could be used to estimate the prob- 

 able therapeutic value of antipneumococcic serum. 



The qualification made by Felton in respect to the freshness of 

 the serum sample as influencing precipitation and protective titer 

 was confirmed by Valentine, McGuire, Whitney, and Falk (1931 ) 1443 

 in experiments on the effect of ageing on antibodies in dried anti- 

 pneumococcic serum. At room temperature, agglutinin and pre- 

 cipitin titer decreased to a greater degree than did the number of 

 mouse-protective units, although the deterioration of the two first- 

 named antibodies failed to take place at ice-box temperatures. 



In a more recent publication (1936), Barnes, Clarke, and 

 Wight 82 compared the unit value of serums obtained by mouse 

 protection with a) the water test; b) agglutination test; c) the 

 authors' routine precipitation test; d) the optimal proportions 



