630 



SCIENCE 



[N. S. Vol. LII. No. 1357 



But in emphasizing' tliese two triumphs of the 

 empiric period long antedating the experi- 

 mental epoch in medicine, sight should not 

 be lost of the essential point, namely that the 

 virtues of those remedies were established also 

 by experiment caiTied out over long decades 

 and upon man himself, for in no other way 

 could these active drugs have been separated 

 from the thousands of innocuous or even 

 harmfid ones applied by man at all stages of 

 his evolution to the alleviation of suffering. 



In a strict sense, curative serums are ex- 

 amples of chemotherapy, and tlie most specific 

 ones known, since they are so exactly adapted 

 to combat a given microbe or its toxin, and 

 because in the end the active component is 

 chemical in character. But as usually em- 

 ployed, the term is applied rather to chem- 

 icals or drugs not produced by the animal 

 body and of definite and ascertainable ulti- 

 mate composition. 



The beginnings of the experimental science 

 of chemotherapy are very recent, and hardly 

 more than a start has been made in exploring 

 the field. The principle on which it is based 

 can be expressed simply: microbic parasites 

 on invading the animal body arouse defensive 

 activities on the part of the host, which when 

 of sufficient intensity serve to weaken and 

 restrain, and ultimately t)o overthrow and 

 conquer the invaders. These natural defend- 

 ers, as we learned earlier, consist of fluid and 

 cellular constituents of the body, sometimes 

 preformed, sometimes only, manufactured on 

 demand, and in part especially adapted to the 

 particular parasitic agent to be vanquished. 



With this picture before them, of the man- 

 ner of the body's defense against microbic 

 invasion, bacteriologists could appreciate that 

 the overcoming and healing of infection is 

 never a mere passive process, and the action 

 of healing agents in the body does not occur, 

 as the older therapeutists believed, precisely as 

 would happen if the parasitic agent could be 

 exposed to the effects of drugs, say in a test 

 tube. Moreover, it was always evident that 

 such effective drugs as quinine and mercury 

 must be employed sparingly, because while they 

 were able to injure and thus to lead to the 



destruction of the microbes inducing malaria 

 and syphilis, they were likewise capable of 

 injuring the component cells of the body 

 itself. 



The outstanding instance in which experi- 

 mental chemotherapy has registered a great 

 success is in connection with the organic com- 

 pounds of arsenic, which have been adapted 

 to the overcoming of infection induced on the 

 one hand by spirochetes and on the other by 

 trypanosomes. That arsenical compoimds pos- 

 sess therapeutically active properties against 

 these two classes of parasitic diseases — as rep- 

 resented on the one hand by syphilis and on 

 the other by African sleeping sickness — is not 

 entirely a recent discovery; but until the sys- 

 tematic investigations of Ehrlich were insti- 

 tuted, which ultimately yielded salvarsan, 

 knowledge was fragmentary, medical practise 

 based on it ineffective, and the road to prog- 

 ress obscure. Now the outlook is wholly 

 changed, and there is going forward an active 

 and either already successful or at least highly 

 promising search for new drugs or chemicals, 

 directed against both the bacterial and the 

 protozoal parasitic microbes. This territory 

 so newly opened to exploration in which or- 

 ganic chemists and pathologists should pool 

 interests in order to move forward, is of al- 

 most infinite possibility, since the number of 

 chemicals is nearly limitless which can be pro- 

 duced and so fashioned as to injure and sub- 

 due as it were the parasitic invader, and at 

 the same time, pass over and leave little in- 

 fluenced the adjacent body cells. But the con- 

 ditions of the search are intricate since, as 

 just indicated, a useful drug must exhibit 

 high power of attack upon the protoplasm of a 

 parasitic microbe and a low one on that of 

 the cells of the blood and the organs, in order 

 that the former and not the latter may be 

 predominately affected. It is a peculiarity 

 of chemicals as contrasted with serums that 

 they can never be so accurately designed to 

 their purposes as to remain entirely without 

 effect on the cells of the host; but it is also 

 recognized that when the drugs are effective, 

 the.y do not carry on a single-handed combat, 

 but serve best when they either assist or are 



