5o THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
discontinued after a varying length of time the parasites reappeared, the disease pursued 
its normal course, and the majority of the animals died. Some few recovered, but the 
animals were not rendered immune, as Laveran proved by reinoculation. 
He had, however, been able to keep infected rats alive for periods many times 
exceeding those of untreated animals. Laveran and Mesnil record very 
unfavourable toxic effects with the ordinary preparations of arsenic. At McGill and 
Liverpool, in our hands the experiments showed the same toxicity of the drug, the 
tendency to cause ulcers and extensive sloughing despite all asceptic precautions. 
The results obtained as to the prolongation of the animal's life was the same. On the 
arrival of natives suffering from Trypanosomiasis it was felt that some form of arsenic 
treatment was indicated. Subcutaneous inoculations of sodium arseniate caused 
so much pain that this form of medication was abandoned. Broden had reported 
the favourable results obtained by the administration of arsenic in the form of Liquor 
Fowleri. Resource was made to this form of the drug, but the surviving natives were 
sent back, to the Congo before the effects of the different preparations could be 
determined. 
Animals infected with the various pathogenic trypanosomes were subjected to 
treatment ; it was found that with sodium arseniate, the most useful form of arsenic, 
sloughing was prone to occur. In such a case the animal very often became so 
depleted by the ulceration that it succumbed to a secondary affection. Moreover, 
the use of arsenic in the form of sodium arseniate is all too apt to cause toxic effects. 
The administration of the preparation may be continued for some time, favourable 
results occur and then, unfortunately, toxic symptoms appear. If the drug be 
discontinued on account of the untoward symptoms the parasites very quickly make 
their reappearance and the animal dies. Moreover, despite medication being 
continued, the parasites which have disappeared will reappear and continue to be 
present and even augment. In such cases an increased amount of arsenic will not 
affect the termination of the disease. We have, therefore, to realise that the ordinary 
arsenic compounds when administered only produce a temporary, favourable effect, 
that, if long continued, the animals will die either from the parasite or from the 
arsenic or from both. Hence, some other compound is indicated. It is for this 
reason that the newer compounds of arsenic have been experimented with in 
order to find a preparation capable of being used over a long period and in high 
doses without producing toxic symptoms. Of the various preparations tried, a meta- 
arsenic anilin compound, atoxyl, has proved the most satisfactory, but it is not ideal. 
It is not non-toxic as dogs, kittens, guinea-pigs, and rabbits have shewn toxic symptoms 
and succumbed, but it is not so toxic as sodium arseniate. It does not produce the 
sloughing which so often follows the subcutaneous or intravenous inoculation of 
sodium arseniate, it causes no pain, and its administration can be continued over a 
period of many months even when used in extremely high doses. 
