616 BIOLOGY OF PNEUMOCOCCUS 



logical similarities or differences between the polysaccharides of 

 the present pneumococcal types and the polysaccharides of other 

 bacteria and non-living substances? 



What is the importance of the chemical configuration of the 

 molecule as a whole and the role of determinant groups in orienting 

 the specificity of the immune response in animals? What is the na- 

 ture of the chemical processes in the bodies of animals of different 

 species which deal with one and the same antigenic substance in 

 such diverse ways after it reaches the tissues? For example, it is 

 possible that a complex antigen may be broken down to non-anti- 

 genic form or to a simple hapten-like substance, so modified by 

 conjugation or synthesis within the tissues that it acquires new 

 antigenic properties — the result depending not only upon the 

 chemical nature of the substance introduced and the route of its 

 administration, but also upon the chemical changes brought about 

 in the particular tissue or animal species tested. 



These are some of the problems that confront the chemist and 

 the immunologist. Perhaps the isolation of specific polysaccharides 

 from pneumococci of the remaining unstudied types, from unre- 

 lated organisms, and from other sources, and an investigation into 

 the more minute details of the molecular mosaic of these higher 

 carbohydrates, may provide clues to the solution of some of these 

 problems. 



The fact that bacterial enzymes capable of decomposing capsu- 

 lar polysaccharides of the different pneumococcal types have more 

 avid and more discriminating selective affinities for capsular poly- 

 saccharides than homologous antibodies have for specific antigens, 

 may lead to the clarification of some of the questions of chemo- 

 immunological specificity. 



VIRULENCE 



Why a strain of Pneumococcus should be virulent for one spe- 

 cies of animal and avirulent for another is a question that awaits 

 answer, and the question is not a simple one. There are the ele- 



