ANTIBODIES TO PNEUMOCOCCUS 357 



lated bacterial species and to the serological classification of pneu- 

 mococci. 



In 1902, Neufeld 974 took exception to some of his predecessors 

 who had studied agglutination of pneumococci with specific serum. 

 He excluded any experiments in which only thread-like growths 

 were observed, and contended that in none of the previous studies 

 was the serum diluted, nor were the observations made soon enough 

 after the organisms and immune serum were mixed. It was in this 

 communication that Neufeld first described the Quellung effect 

 which appeared when homologous immune serum was added to 

 pneumococci. Neither normal rabbit nor normal human serum 

 agglutinated pneumococci but normal beef serum often caused 

 clumping of the organisms. Neufeld also noted that dead as well as 

 living pneumococci were susceptible to the clumping action of im- 

 mune serum, and that in the reaction the cocci were not dissolved 

 nor were the living organisms killed. Neufeld met with difficulties in 

 preserving the agglutinative titer of some samples of immune rab- 

 bit serum — a difficulty later experienced by Hintze (1921 ) 647 and 

 others with rabbit serum. More recently, Valentine, McGuire, 

 Whitney, and Falk (1931) 1443 reported that the agglutination 

 titer of dried antipneumococcic serum kept at room temperature 

 decreased more rapidly than the mouse-protective titer. However, 

 when the desiccated serum preparations were preserved at ice-box 

 temperatures, the potency of the serum in this respect was not ap- 

 preciably affected. 



AGGLUTININS IN THE BLOOD OF PNEUMONIA PATIENTS 



The serum of patients convalescing from pneumonia was in some 

 cases found by Neufeld to contain agglutinins. Sometimes their ap- 

 pearance was observed shortly before crisis although the aggluti- 

 nating power of convalescent serum was highest on the day after 

 crisis. The later observation was duplicated in the same year by 

 Huber, 663 who also reported that the agglutinative properties of 

 convalescent serum progressively diminished and completely dis- 



