810 



SCIENCE 



[N. S. Vol. XXXII. No. 832 



died last October, requesting him to assist 

 in this work by furnishing the material 

 necessary for the experiments. As the 

 desired substance was then unknown, 

 it was proposed to synthetize it by al- 

 lowing nitrosodimethylanilin to react on 

 metaoxydimethylanilin. This latter body 

 being likewise unknown had to be pre- 

 pared. Naturally the chemical thus orig- 

 inated was employed not only for the 

 purpose suggested by Ehrlich, but also for 

 all reactions for which analogous products 

 had been previously used. One of the first 

 experiments made was to try it in place 

 of resorein, to which it is closely related. 

 The principal use of resorein in the color 

 industry was the manufacture of fluores- 

 cein by fusing it with phthalic acid anhy- 

 dride. Prom fluorescein was made eosin, a 

 particularly fine coloring matter. The 

 Ehrlich product, however, gave in the 

 same reaction a color even superior to 

 eosin, namely, rhodamine, and in another 

 reaction it furnished Nileblue. 



Although originally a physician, Ehr- 

 lich, through steady pursuit of our science, 

 developed into a most proficient and in- 

 genious chemist, and by combining physio- 

 logical with synthetic chemistry he created 

 on their borderland the new science of 

 chemotherapy. 



To demonstrate to you the nature of 

 chemotherapy, it is perhaps best to show 

 what has hitherto been accomplished by 

 Ehrlich and his school. 



In the development of bacteriology, the 

 science upon which are based the most im- 

 portant advances of modern medicine, the 

 coal tar colors have played an indispen- 

 sable part. These dyestuffs made possible 

 the discovery of the dreaded microbes and 

 their detection in disease. It was found 

 that different bacteria manifested a select- 

 ive affinity for different colors, some ab- 

 sorbing one and some the other, and this 



in itself now enables the scientist to dis- 

 tinguish between organisms belonging to 

 the same group. 



We know now that many, if not most, 

 diseases are of parasitic origin, and that 

 man and other animals are constantly at 

 the mercy of these invisible enemies. 

 Though attention has been devoted chiefly 

 to the bacteria which belong to the lowest 

 forms of vegetable life, modern research 

 has brought to light the fact that certain 

 diseases are due to protozoa or animalcules, 

 which, on the other hand, constitute the 

 lowest stage of animal existence. Among 

 these disease-producing protozoa the most 

 important that have thus far been discov- 

 ered are the Plasmodium, which causes 

 malaria, the trypanosoma, a parasite 

 which produces the African sleeping sick- 

 ness, the . ameba of dysentery, and the 

 spirochete, the causative agent of syphilis. 



It is a curious circumstance that al- 

 though protozoa were discovered in the 

 blood of various animals as far back as 

 sixty years ago, that is even before the 

 birth of bacteriology, it is only within the 

 last ten years that their important role in 

 the causation of disease has been appreci- 

 ated. A number of causes have contrib- 

 uted to this, especially the fact that most 

 of the maladies due to protozoal parasites 

 occur in tropical countries, while bacterial 

 diseases are constantly in our midst. The 

 discovery of the malarial protozoa, the 

 Plasmodium, by Laveran, however, gave 

 an impetus to this line of research, and 

 this circumstance in connection with the 

 special study that is being devoted to trop- 

 ical diseases has already contributed ma- 

 terially to our knowledge of the origin of 

 many hitherto obscure maladies. 



More important than the discovery of 

 the cause of a disease, however, is its pre- 

 vention and cure. Fortunately, in the 

 case of malaria empirical observation had 



