618 BIOLOGY OF PNEUMOCOCCUS 



stances antagonistic to the activity of the antibodies and limiting 

 the protective action of the serum. By what means can these in- 

 hibitory substances be neutralized or eliminated? 



Are the zonal effects observed in serological reactions and in 

 protective experiments ascribable wholly to the capsular polysac- 

 charide of Pneumococcus or may they be, in part at least, pro- 

 duced by serum lipids? To what extent are these effects dependent 

 upon the quantitative relations existing at the time between anti- 

 gen and antibody and the solubility of the immune complex so 

 formed? 



CHEMOTHERAPY 



A suitable and harmless drug with high selective affinity for the 

 protoplasm or capsular substance of Pneumococcus is wanting. 

 The field of chemotherapy in pneumococcal infections, promising 

 as it is, abounds in difficulties. The narrow limits between poison- 

 ous, untoward effects and therapeutic action in the animal body, 

 the selective affinity of the agents for somatic protein or capsular 

 carbohydrate of bacteria, and the action of the drug in inhibiting 

 some essential physiological function, impairing the metabolic 

 processes, or bringing about morphological changes in both bac- 

 terial and body cells, are problems that should entice rather than 

 discourage the investigator. 



At present, cinchona would appear to offer a promising source 

 from which to prepare agents capable of specific pneumococcidal 

 action. In the myriad of compounds now being synthesized in the 

 chemical laboratory a key substance may be found. 



IMMUNOLOGICAL RESPONSE 



The comparative response of animals of different species to the 

 introduction of pneumococcal antigens by diverse parenteral 

 routes perplexes the immunologist. Antigen injected into the skin 

 of the rabbit results in the appearance of species-specific but not 

 of type-specific antibodies in the serum; antigen injected into a 



