246 CHE MO THERA P Y 



The earlier investigations in this direction were, however, not 

 crowned with success, and it was soon realized that in these studies 

 also, accident would probably have to play a role, unless indeed 

 every chemical substance were individually tested. The first and 

 most formidable difficulty which was encountered depended upon 

 the fact that the majority of those substances which have strong 

 germicidal properties, when tested outside of the animal body, were 

 promptly rendered innocuous by entering into chemical combination 

 with the albumins of the blood, when introduced into the body, 

 and if a certain dose was exceeded their toxic effect was such that 

 any attempt at destruction of the parasites would have carried 

 with it the destruction of the host. I well recall an interesting 

 observation which illustrates this point. A patient suffering from 

 pneumonia was accidentally given a dose of bichloride of mercury 

 which nearly caused the individual's death. He was saved with 

 difficulty, but died of his pneumonia a few days later. Evidently 

 the dose of the bichloride, though large enough to have nearly 

 killed the patient, had not been sufficiently large to kill the offending 

 parasites. 



Organotropism and Parasitotropism. In work of this nature, the 

 distribution of the poison in the body is evidently of prime impor- 

 tance. If, aside from any binding action on the part of the circulating 

 albumins, the affinity of the poison is greater for the tissues of the 

 body than for the protoplasm of the parasites, or to use the parlance 

 of Ehrlich, if the poison is more markedly organotropic than parasito- 

 tropic, it is evidently not suitable for therapeutic purposes, and 

 especially so, if at the same time the toxic dose for the macroorgan- 

 ism should be smaller than that for the microorganism. The great 

 problem then has been to discover substances which, while possessed 

 of germicidal properties, or what amounts to the same thing, of the 

 power to inhibit reproduction of the parasites, shall also be non- 

 toxic, or but little toxic for the macroorganism, and more markedly 

 parasitotropic than organotropic. 



In this investigation, Ehrlich, to whom we are already indebted 

 for so much of our knowledge of the more intricate problems of cell 

 life, has again taken the leading position, and may indeed very 

 appropriately be styled the father of modern pharmacology and 

 chemotherapy. Since the degree of antibody formation in systemic 

 infections with protozoan parasites, in contradistinction to bacterial 



