CLASSIFICATION OF PNEUMOCOCCI 133 



ing chapter, transformation of a strain of one type into an organ- 

 ism of another type can be accomplished by appropriate treat- 

 ment of the culture. 



The particular serological type to which a pneumococcus be- 

 longs may be determined in several ways. The agglutination, pre- 

 cipitation, complement-fixation and mouse-protection tests, or 

 combinations and modifications of these tests, may be applied to 

 disclose the type identity of a strain, but it is safe to conclude 

 that for routine needs the Neufeld method for determining specific 

 types of Pneumococcus should be the one of choice. It gives an an- 

 swer in the shortest time, possesses a high degree of accuracy, and 

 is simple to perform. It makes for a saving in expense and elimi- 

 nates the necessity of using mice. Whenever the results are not 

 clear or when any doubt exists as to the type to which the organ- 

 isms belong, the mouse-heart-blood or mouse-protection test should 

 always be carried out for confirmation. Before hope of type iden- 

 tification is abandoned, the more refined methods such as that of 

 Amoss should be tried. The usual cultural procedures, carbohy- 

 drate fermentations — especially of inulin — and bile-solubility tests 

 are always to accompany the bacteriological diagnosis when un- 

 certainty arises. For clinical diagnosis and for the direction of se- 

 rum administration, as well as for epidemiological studies, labora- 

 tories should be prepared to run their cultures through the series 

 of the thirty-two known serological types. The procedure requires 

 a supply of potent, monovalent type-specific immune serums, pref- 

 erably prepared by the immunization of rabbits with standard 

 type strains. With type-specific serums, accurately prepared re- 

 agents, healthy laboratory animals, and careful bacteriological 

 manipulations, there should be few cultures that cannot be sero- 

 logically classified within the known fixed types. 



