HISTORY OF PNEUMOCOCCUS 29 



creatures ; and such a serum gave an early promise of mitigating 

 pneumococcal affections in man. 



The first glimpses of the vagaries of microbic behavior under 

 varying environment were later to expand into broader views of 

 that instability of bacterial characters which result in dissociation 

 into varied and distinct forms or possible mutation into alien spe- 

 cies. These discoveries were to clarify our ideas concerning viru- 

 lence and the consequent infectiousness of a bacterium for a sus- 

 ceptible host. The fact that the serum from animals treated with 

 Pneumococcus or some of the derivatives of Pneumococcus pos- 

 sesses the property of clumping this organism was, at the hands of 

 Neufeld, Dochez, and Gillespie, and later of Cooper and her asso- 

 ciates, to form the basis for a method of separating the members 

 of a supposedly homogeneous species into thirty or more clearly 

 defined and serologically specific types. This biological classifica- 

 tion was to give a new aspect to the problems perplexing the epi- 

 demiologist, the bacteriologist and immunologist, and the clinician. 



For a time Pneumococcus investigation was to lag, and then, 

 stirred by the contributions of Neufeld and of the Cole school, it 

 was to receive a new impetus, and to bring the vital activities of 

 this amazing cell more clearly into sight. The facts that have been 

 disclosed in this new and closer view, their bearing on general bio- 

 logical problems, and their application to the development of pre- 

 ventive and curative agents will be related in subsequent chapters. 



