146 CONTEMPORARY SCIENCE 



to subdue a particular kind or class of infection. The 

 beginnings of chemotherapy reach into the dim past; the 

 science of chemotherapy is just being built up. The 

 epochal discoveries of the curative value of cinchona bark 

 in malaria and of mercury in syphilis, are examples of the 

 early, and as we now say empirical working out of speci- 

 fic therapeutics. But in emphasizing these two triumphs 

 of the empiric period long antedating the experimental 

 epoch in medicine, sight should not be lost of the essen- 

 tial point, namely that the virtues of those remedies were 

 established also by experiment carried out over long dec- 

 ades and upon man himself, for in no other way could 

 these active drugs have been separated from the thousands 

 of innocuous or even harmful ones applied by man at all 

 stages of his evolution to the alleviation of suffering. 



In a strict sense, curative serums are examples of 

 chemotherapy, and the 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 employed, the term 

 is applied rather to chemicals or drugs not produced by 

 the animal body and of definite and ascertainable ultimate 

 composition. 



The beginnings of the experimental science of chemo- 

 therapy 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 to overthrow 

 and conquer the invaders. These natural defenders, as 

 we learned earlier, consist of fluid and cellular consti- 

 tuents of the body, sometimes performed, 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 manner of the 

 body's defense against microbic invasion, bacteriologists 



