1909.] Antimony Compounds in Trypanosomiasis in Rats. 253 



by boiling without any cloudiness resulting. It is a very efficient 

 trypanocide and causes no local irritation in the rat. After the injection of 

 1 c.c. of a 0"2-per-cent. solution* into rats of 100 to 200 grammes weight, 

 trypanosomes, though previously numerous, entirely disappear from the 

 peripheral blood within one to two hours. Estimated by the amount of 

 antimony present in the solutions, the ethyl is more powerfully trypanocidal 

 than the sodium salt, which may suggest either that less is deposited at the 

 point of application, or that it reaches the trypanosomes in a more readily 

 penetrating form. 



Though more poisonous to the rat than sodium antimonyl tartrate, the 

 range of dose, or the difference between the effective trypanocidal dose and 

 the lethal dose, is not less than that of the other antimony preparations. 

 The optimum dose may be found to correspond to Browning's therapeutic 

 dose, viz. : two-thirds of the maximum dose that average animals tolerate. 



From our own work, and that of others, we think that sufficient data have 

 been obtained to indicate some points which must be taken into consideration 

 in attempting further advance in the treatment of trypanosomiasis : — 



(1) As regards the compound it must be non-irritant and capable of 

 remaining in perfect solution at the temperature and alkalinity of the 

 tissues. 



(2) It must act quickly on the trypanosomes, for otherwise these parasites 

 seem to acquire a tolerance to it. It is possible that some drugs may 

 require to be altered in the tissues before they begin to affect the parasites ; 

 but with this proviso, we suggest, as a working rule, that no drug which, 

 given in full therapeutic dose, does not destroy the trypanosomes in the 

 blood within two hours is likely to prove an advance on remedies already 

 in use. 



(3) When the trypanosomes have been expelled from the blood by a single 

 full therapeutic dose, there must be no recurrence in the majority of cases 

 within some fixed time, which will vary with the particular host, and the 

 species and strain of trypanosome in use ; the length of this period must be 

 determined by each investigator by reference to some of the known 

 trypanocides. In our experiments it proved waste of time to persevere with 

 any drug whose administration in a single full dose was followed by 

 a recurrence in the majority of cases within a week. The longer the time 

 during which there is no recurrence in the majority of animals treated the 

 more promising is the outlook for the drug under trial. But the non- 

 recurrence in a single individual is of comparatively small importance. 



In our experiments the majority of the rats that survived the injection 

 * The strength of the solution was ascertained by estimation of the antimony. 



