PRODUCTION OF ANTIPNEUMOCOCCIC SERUM 593 



tion of pneumococci into groups was accomplished by Dochez and 

 Gillespie, serum therapy of lobar pneumonia was purely empirical 

 owing to the lack of exact knowledge concerning the diversity of 

 pneumococcal strains. The separation of pneumococci into thirty- 

 two distinct types and the recent development of the Neufeld 

 Quellung reaction as a method of type determination have ren- 

 dered serum therapy far more rational, effective, and economical 

 than formerly. For many years, monovalent, immune horse serum 

 was employed in the serological diagnosis of pneumococcal types, 

 but now the Neufeld technique employing immune rabbit serum for 

 the demonstration of capsular swelling yields more satisfactory re- 

 sults, besides being more rapid than the agglutination or other re- 

 actions involving the use of immune horse serum. 



IMMUNE HORSE SERUM 



Diagnostic serums may be produced by immunizing horses with 

 type-specific strains of pneumococci by the same methods followed 

 in the production of therapeutic serum. In laboratories where mono- 

 valent therapeutic serums are manufactured it is convenient to se- 

 lect bleedings, usually the earlier ones, and, if tests are satisfac- 

 tory, to utilize the serum for type identification. In determining 

 the suitability of immune horse serum for diagnostic purposes, the 

 specific agglutinin titer, the presence of heterologous agglutinins 

 for other pneumococcal types (particularly those of closely re- 

 lated types), and the velocity of the agglutination reaction are to 

 be considered. For these tests it is essential to use organisms of 

 maximal virulence, and preferably young, living cultures. The 

 macroscopic method of agglutination is satisfactory, and readings 

 should be taken at frequent intervals during the first two hours. 

 Serums that are suitable for diagnostic use usually give clear-cut, 

 specific agglutination in relatively high dilutions after one-half- 

 hour's incubation in a water-bath at 37°, and exhibit no visible 

 agglutination with representative strains of other types, although 

 serums that show some non-specific agglutination in dilutions well 



