ANTIBODIES TO PNEUMOCOCCUS 



379 



precipitation test ; e) Felton's test for combining equivalents ; and 

 f) a modified precipitation test devised by the authors. The fol- 

 lowing table taken from page 131 of the authors' communication 

 shows the correlations found between precipitation, combining 

 equivalents, agglutination, and mouse protection. 



Not applicable. 



By closely spacing the serum dilutions in the modified test, 

 Barnes, Clarke, and Wight succeeded in obtaining precipitin titers 

 which agreed more closely with estimations of the mouse-protec- 

 tive value than with any of the other methods tested. It would 

 seem, therefore, that the precipitin content, as determined by this 

 method, is in close agreement with the amount of protective anti- 

 body in specific antipneumococcic serum. 



