286 MICROBES AND TOXINS 



living creature because it kills the cells of the organs at the 

 same time as the bacterial cells. Quinine is a good thera- 

 peutic agent because it destroys the parasites of the red 

 corpuscles without acting at least in general on the 

 corpuscles themselves. 



There are cases where the sterilization of a tissue may be 

 performed without the least inconvenience. Mercury is the 

 traditional remedy in syphilis* its internal application is 

 limited by its toxicity ; but after a contact possibly dangerous, 

 it may be applied as a prophylactic to the skin. Metchnikoffs 

 experiments on the chimpanzee and on man have proved 

 that simple rubbing with calomel ointment sterilises the skin 

 where the microbe of syphilis has just been inoculated and 

 prevents infection. This preventive treatment, which is as 

 efficacious as it is simple, is already practised. 



Origins. The renaissance of chemiotherapy has had 

 several causes. The first is the revolution due to Pasteur's 

 teaching. When a disease is found to be due to a germ, to a 

 germ which is known and which can be made to transmit the 

 disease by inoculation into a laboratory animal, then there is 

 room for experimental therapeutics. Animal experiment 

 permits us to go much further than clinical observation. 

 Nevertheless, the progress of microbiology at first seemed about 

 to throw drug therapy into the background. Marvellous 

 biological remedies were discovered, both preventive and 

 curative, surpassing in specificity and efficacy all the drugs of 

 the Pharmacopoeia, e.g. the Pasteur vaccine against anthrax, 

 vaccination against rabies, and all the serotherapies. The idea 

 at once suggested itself that all infectious diseases might be 

 treated in similar ways. 



But that has not proved to be the case ; there is a group of 

 infectious diseases against which vaccination and serotherapy 

 have achieved nothing or almost nothing, the protozoal diseases. 

 In no case has the serum of an animal susceptible to the 

 trypanosome of sleeping sickness, and immunized against this 

 microbe, been capable of exerting a curative effect upon the 

 experimental disease in other animals. In malaria, all the 



