580 BIOLOGY OF PNEUMOCOCCUS 



of the anticarbohydrate precipitins, using capsular polysaccha- 

 ride prepared by the early method of Heidelberger, Goebel, and 

 Avery. 613 The soundness of the argument appears questionable in 

 view of the more recent experiments of Avery and Goebel (1933) 46 

 with acetyl polysaccharide. Ward (1932), 1483 after using the sen- 

 sitive bactericidal test in determining the phagocytic power of 

 SSS-absorbed serum, concluded that there was no necessity to 

 predicate the presence of an additional and possibly non-antibac- 

 terial antibody in immune serum. Other evidence advanced by 

 Sabin to support his hypothesis depended upon tests with serum 

 prepared or utilized in different ways in treating the dermal pneu- 

 mococcal infection in rabbits, but the results failed to parallel 

 those of the mouse protection tests. 



Some antipneumococcic serums are therapeutically more active 

 than others and the differences may possibly be due to the presence 

 or absence of antitoxic or non-antibacterial substances in addition 

 to the mouse protective antibody. Felton, 404 however, doubted the 

 evidence put forward in support of this hypothesis. Claims for 

 extra-therapeutic properties of serum based on tests in rabbits in- 

 fected intradermally are subject to the limitations of the method. 



IN VITRO TESTS 



Various means have been employed for titrating the antibody 

 content of antipneumococcic serum without resorting to the use of 

 animals. Thus, tests for determining the amount of water-insoluble 

 proteins, the complement fixation and bactericidal reactions, floc- 

 culation with toxic preparations, and the Quellung reaction, in ad- 

 dition to agglutination and precipitation tests have been devised 

 for the purpose. 



Water test. The so-called water test was an outgrowth of the 

 observation by Felton (1924) 396 that simple dilution of serum with 

 water resulted in precipitation. It was thought that the amount of 

 precipitate so formed was an indication of the protective strength 

 of the serum and, furthermore, that the method could be used to 



