36 



STRONG AND TEAGTJB. 



treatment was given and at no time subsequently have the parasites 

 reappeared. From Table I it is seen that the minimum lethal dose 

 is from 0.22 to 0.26 grain, which is more than twice the dose shown 

 to be efficacious in producing a cure in monkeys. 



These experiments, therefore, show conclusively that monkeys, Cyno- 

 molgus philippinensis Geoff., can be cured permanently of surra infection 

 by a single injection of arsenophenylglycin. 



EXPERIMENTS IN HORSES. 



Early in the year 1909 attempts were made to treat horses infected 

 with surra and brought to the laboratory. The animals were placed in 

 a small screened stable where they were not kept under the best hygienic 

 conditions. Here their weight could only be estimated approximately, 

 and hence the dosage of the drug administered could not be projjerly con- 

 trolled. Many of the horses died from the toxic effect of the drug ; others 

 during the course of the treatment suffered a relapse of the infection 

 and were either killed or succumbed during further treatment. In some 

 instances a relapse occurred after the animal had survived a large 

 initial dose. The repeated administration of small doses of arsenophe- 

 nylglycin gave very unsatisfactory results. None of these animals sur- 

 vived. Later we were able to obtain the weight of 5 horses before 

 beginning treatment, with these the results were as follows : 



Weight of horse. 



Dose in 



grams 



per kilo. 



Remarks. 



460 kilos 



0.05 

 . 052 

 .058 

 .065 

 .006 



Recovered from effects of drug. 



Died in 8 days. 



Recovered. 



Died suddenly 24 days later. 



Died in 2 days. 



580 kilos 



521 kilos 



430 kilos 



371 kilos 





From these preliminary experiments it appears that the minimum 

 lethal dose for a large American horse is about 0.052 gram per kilo. A 

 horse which died after receiving this amount per kilo was a very fat 

 animal which had been foundered, so that the dose was actually relatively 

 higher than the figures indicate. 



Our experiments indicate, therefore, that the minimum lethal dose 

 per kilo of body weight is about three times as great for monkeys as it is 

 for horses. 



Moore offers the following explanation for ,the discrepancies in dosage between 

 large and small animals when calculated on the basis of the body weight. He 

 emphasizes the fact that the seat of biochemical activity after the administration 

 of arsenic or antimony is in the intestinal mucosa and that it would seem prob- 

 able that this is also the seat of manufacture of the trypanocidal substance. In 

 the larger animals the therapeutic dose is therefore lowered because of the rel- 



