Treatment. 803 



eously). Similarly Holmes observed excellent curative results in horses 

 affected with surra, after the use of arsenious acid. However in order 

 to make the recovery complete all trypanosomes, even the latent forms 

 in the internal organs must be destroyed (therapia sterilisans magna), 

 therefore the remedy should be used in as heavy doses as possible, that 

 is in sub-toxic doses (as formerly the arsenic has been used in too small 

 doses, and the parasites which were not destroyed were capable of 

 causing relapses). The good results obtained with the auripigment can 

 also be explained by the fact that it usually contains free arsenious acid. 

 In the experimental treatment it was further observed that the 

 trypanosomes are capable of adapting themselves to the remedies under 

 discussion, for instance trypanosomes which, after atoxyl treatment 

 with incomplete recovery, remain alive in the animal and later again 

 multiply, are no longer influenced by the same remedies, and likewise 

 not by other derivatives of phenyl arsenious acids. This resistance is 

 transmitted by sul)sequent passages through the same species of animals 

 from generation to generation. This condition may become objection- 

 able in practice, inasmuch as from animals which have been subjected 

 to such specific treatment and which have not completely recovered, flies 

 may later transmit to other animals atoxyl- (arsenic-, trypanblue-, 

 fuchsin-, etc.) resisting trypanosome strains. Such animals then resist 

 treatment with the same or with a related remedy. Most recently how- 

 ever Ehrlich succeeded in producing new arsenical preparations, the 

 arsenophenyglycin, and the above-mentioned arsenobenzol, which, with 

 a slight toxicity for mammals are capable of attacking even arsenic- 

 resisting strains of tryponosomes and which have also otherwise proven 

 most satisfactory for trypanosome affections out of the great number of 

 chemicals that have been tested. 



Ehrlich aimed to explain the inechauism of the specific therapeutic action 

 through certain groupings (chemoeeptors) in the protoplasm of the trypanosomes, 

 which possess for certain chemical substances, for instance for the trivaleut arsen 

 as it occurs in arsenical acids, a special affinity, ami are capable of anchoring 

 such to the plasma. The resistance of already treated strains may result from 

 the fact that the respective chemoeeptor experiences a reduction of its affinity to 

 the applied remedy, therefore its resistant strain is destroyed only by a greater 

 quantity of the remedy, or by a more strongly avidious remedy, for instance the 

 arsenophenylglycin. 



Based on these experimental results, which have repeatedly 

 been substantiated especially by Uhlenhuth, Hubener & Woithe 

 for the treatment with atoxyl of experimental dourine, by 

 Loeffler with arsenic in experimental nagana, by Levaditi and 

 his co-^vorkers for the action of atoxyl on various strains of 

 trypanosomes, arsenical preparations are used in practice for 

 the treatment of these diseases. They are employed either 

 combined wdth each other, or alternately; further antimony 

 preparations, especially tartar emetic, and wdtli these treat- 

 ments satisfactory results are generally obtained, or at least 

 encouragement for further therapeutical experiments. In 

 general, the rule should be observed to administer the remedy 

 as soon as possible after the infection, in a single, or at most 

 in two subtoxic doses, as only in this manner can relapses and 

 the development of hypersensitiveness be prevented. (For 

 details see the individual affections.) 



