CHAPTER XIX. 



CHEMOTHERAPY. 



DEFINITION. METHOD. ATOXYL. SALVARSAN. CHEMOTHERAPY or MALIGNANT 



TUMORS. CONCLUSION. 



Serum therapy proved the fundamental fact that it is possible by 

 the injection of specific sera selectively to destroy or counteract the 

 poisonous effects of certain micro-organisms without in any way injuring 

 the infected host. That similar results are attainable by chemical means 

 is demonstrated by the empirical use of quinine in malaria. For a long 

 time this chemical specific stood in a class by itself. In recent years, 

 the progress made in the study of infections by the protozoa, especially 

 the trypanosomes and spirochetes, and the possibility of transmitting 

 these diseases to the lower animals, stimulated a renewed effort in quest 

 of chemical substances analogous to quinine. Paul Ehrlich led the way 

 in this new direction and termed this study " Chemotherapy " in contra- 

 distinction to "Pharmacotherapy." 



Only those agents can be employed chemotherapeutically in which the 

 " organatrope" and "parasitatrope" relation is favorable, that is, primarily 

 when the curative dose is only a very small fraction of the toxic dose 

 (Ehrlich). In infectious diseases it is the causative parasite that is 

 aimed at, in malignant tumors the tumor cells are the objects for de- 

 struction. In both, however, it is absolutely essential that the normal 

 tissues of the body remain entirely uninjured. 



Thus far the most favorable results of chemotherapy have been ac- 

 complished in trypanosome and spirochete infections. 



Researches under Ehrlich's direction clearly defined that there are three different 

 types of substances which can destroy the trypanosomes : 



(a) The group of basic silk dyes (Fuchsin). 



(b) The group of cotton dyes (Benzopurpurin series) of which trypan red and try- 

 pan blue have proved most efficient. 



(c) The group of arsenical products (atoxyl and its derivatives). 



The basis for differentiating these three classes is seen from the 

 following experiments. If a mouse suffering from trypanosomiasis 

 receives an injection of an active fuchsin preparation, the trypanosomes 

 disappear from the blood. They remain away permanently (" Sterilisatio 

 magna") provided that the injected dose is large enough. The animal 

 is thus cured by a single injection. If the dose is not sufficient, many 



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