CHEMICAL REMEDIES 295 



with chemistry in putting tartar-emetic, i.e., antimony, in the 

 same group as arsenic. 



The resistance acquired towards the bodies of one group 

 presents, however, different degrees ; thus, in the arsenical 

 group a strain resistant to atoxyl is still sensitive to arseno- 

 phenylglycine ; if it is now rendered resistant to this latter 

 substance it still remains sensitive to tartar-emetic and arsenious 

 acid. Again subjected to arsenious acid it becomes resistant 

 to tartar-emetic; no strain, however, has yet been created 

 resistant to arsenious acid. 



These observations have important consequences for practice ; 

 they indicate that it may be necessary to attack the same 

 trypanosome by different remedies and form the reason for 

 the method of combined or alternated drug treatment. The 

 drugs superpose their actions on the parasite, but not necessarily 

 on the body, because their toxicity does not bear entirely on 

 the same organ cells. Further, the different degrees of resis- 

 tance which exist towards drugs of the same group show that 

 it is proper to associate atoxyl and arsenious acid, although 

 they are both arsenical bodies. Attacking the same parasite 

 with several remedies is doing the same, says Ehrlich, as the 

 entomologist who pins out a butterfly with several pins. 



Although the difficulty may be overcome by using these 

 combined treatments the appearance of resistant strains is 

 always a danger. In sleeping-sickness, for example, there is only 

 one good drug, atoxyl, to destroy the trypanosome, and in 

 presence of strains resistant to this, one is rather helpless, the 

 other remedies being either too weak or too toxic. The 

 danger would be aggravated should the trypanosomes preserve 

 hereditarily their acquired resistance through their passages in 

 the tsetse-fly which conveys them. It would represent the 

 creation of a more virulent and less curable disease, not only in 

 an individual, but throughout a whole country. 



Things do not go on in the living body exactly as in a 

 test-tube. This fact, so often referred to already, must be 

 insisted upon again. 



There are certain chemical substances which act on the 



