I.— PHYSIOLOGY. 171 



distribution in the organism, particularly as regards the central nervous 

 system. 



The most satisfactory arsenic compound yet discovered for the cure 

 of trypanosomiasis is tryparsamide. It is less toxic than atoxyl and has 

 a slightly higher therapeutic index ; it has a most marked trypanosidal 

 action in animals and has been used with some success in cases of sleeping 

 sickness from T. Gambiense. One injection causes the disappearance of 

 the parasite from the blood of man, and if the injections are repeated in 

 courses, the cure may be complete. Like atoxyl it affects the eye : even 

 the smaller therapeutic doses cause visual disturbance, and the risk of 

 complete blindness is always present ; perhaps as many as 30 per cent, 

 of all patients treated with this drug suffer from some eye lesions. 

 Tryparsamide is valuable also in certain forms of syphilis, particularly 

 cerebral syphilis : approximately 40 per cent, of the cases of general 

 paresis committed to the State Insane Hospitals in Wisconsin, U.S.A., 

 were restored to sanity (Loevenhart). This action is probably indirect 

 since there is no evidence to show that it is absorbed into the central 

 nervous system more than other organic arsenicals. 



All these organic arsenical compounds must be injected in order to 

 produce a satisfactory effect ; but one compound, m. amino-p. hydroxyl 

 phenyl arsenic acid, acts upon and destroys spirochsetes when taken by 

 the mouth (Levaditi) ; it is generally administered as its acetyl derivative 

 which is known as stovarsol. Stovarsal has been largely used as a 

 preventive to syphilis, but it is now known that it has a remarkable 

 curative action in amoebic dysentery like emetine (Valenti), and that in 

 cases of benign tertiary malaria it checks the attacks and prevents the 

 return of the disease, at all events for many months. 



It was at first thought that, as laboratory animals are so easily infected 

 with trypanosomes, it should be an easy matter to determine which 

 compounds were likely to be most valuable in the treatment of trypano- 

 somiasis ; unfortunately this is not the case, a drug may cure trypano- 

 somiasis in one animal and not another and the crucial tests must always 

 be made on man. Fourneau's o-hydroxy p. acetyl amino-phenyl arsenic 

 acid (270) acts much better on laboratory animals as a cure for trypano- 

 somiasis than tryparsamide, but has not proved so satisfactory as trypar- 

 samide in the Congo for the treatment of sleeping sickness. Since the 

 crucial test with all these compounds must be made in Africa it is obvious 

 that the expense and difficulty of continuing such researches is enormous. 



Most of the antimony derivatives corresponding with the organic 

 arsenicals have been prepared; for example, that corresponding with 

 acetyl-atoxyl, also m. chloro-p-acetyl amino phenyl stibamate of soda 

 (Heyden 471) have been extensively employed in Kala-azar and Bilhartzia. 

 Speaking generally, they have a more powerful action than tartar emetic 

 on such diseases as Bilhartzia, Kala-azar, and Filaria, and to some of 

 them, like sodium antimony thioglycollate, the parasites do not become 

 readily immune. Unfortunately, the organic compounds of antimony 

 have a toxic action on the tissues and are very difficult to administer, so 

 that antimony tartrate or stibamine urea (NH2CO.NH.C6H4SbO(OH)2), 

 a compound which has recently been prepared pure, are generally 

 preferred. 



