MICROBIAL DISEASES OF MAN AND ANIMALS. 679 



and, then, they have become resistant to arsenic so that the patient succumbs 

 in spite of repeated doses of the drug. Many organic compounds of 

 arsenic were experimented with in the hope of finding an efficient trypano- 

 cide and several valuable drugs have been found: "Atoxyl" which is the 

 sodium salt of para-amido-phenyl-arsenic acid, acetylated atoxyl, and arsen- 

 ophenylglycin, are all organic compounds of arsenic; they are much more 

 effective than is arsenic itself. Similar organic compounds of antimony 

 and tartar emetic are almost as effective, while certain aniline dyes have 

 a distinct trypanocidal value. It has been found that trypanosomes may 

 become resistant to any one of these drugs, and that drugs may destroy 

 some stages of the trypanosome while they are unable to destroy others. 

 In order to give the parasites no opportunity of acquiring resistance to any 

 drug, and in order to destroy them at all stages of their development, the 

 following general rules are now observed in the treatment of trypanoso- 

 miasis. The drugs employed should be alternated, and they should be 

 given as early in the disease as possible, and in as large doses as 

 possible. It is possible that these principles will be found to be of value 

 in the treatment of other diseases caused by protozoa. 



The prevention of the disease depends upon the avoidance of the water's 

 edge, where Glossina palpalis exists, and of the proximity of persons in- 

 fected by trypanosomiasis; the most usually successful way of recognizing 

 infected persons is by the discovery of trypanosomes in the fluid aspirated 

 from their enlarged lymphatic glands. 



HUMAN TRYPANOSOMIASIS or SOUTH AMERICA. 

 Trypanosoma cruzi. 



This disease is caused by Trypanosoma cruzi (Endotrypanum cruzi) ; 

 it is transmitted by the bites of a reduviid, Conorrhinus megistus. It 

 has only been found in Brazil. 



The Trypanosoma cruzi may be either free in the blood plasma or lie within a 

 red cell. It multiplies, in the organs, by losing its locomotary apparatus and form- 

 ing a sphere which divides into eight portions: a new trypanosome develops from 

 each portion. 



The disease is a chronic one, characterized by irregular temperature, 

 by wasting, oedema, and enlargement of the spleen and lymphatic glands. 

 It is often fatal. It may be prevented by avoiding the insect which trans- 

 mits it; the habits of the Conorrhinus resemble those of a bed bug. 



