19 



Some Experiments with Arsenphenylglycin and Trypanosoma 

 gambiense in Glossina palpalis. 

 By H. L. Duke. 



(Communicated by Sir John Eose Bradford, K.C.M.G., Sec. U.S. Received 

 September 28,— Read November 14, 1912.) 



The experiments detailed below were devised with a view to investigating 

 the action of arsenic in the form of arsenphenylglycin upon Trypanosoma 

 gambiense as carried by Glossina palpalis. It was found convenient to deal 

 with the subject under four separate enquiries — 



I. Does the presence of arsenic in the blood ingested by a positive fly 

 destroy the trypanosomes in that fly ? 



II. Does preliminary feeding of flies on blood containing arsenic have any 

 effect on the subsequent development of trypanosomes in their interior ? 



III. If flies are fed on blood containing arsenic shortly after the infecting 

 feeds on a gambiense monkey, are the flagellates still capable of development 

 in the fly ? If they can still develop, is the resultant strain arsenic-resistant 

 in the blood ? 



IV. Has arsenphenylglycin any prophylactic action against the bite of 

 a fly infected with T. gambiense, and, if so, what is the extent of this 

 protection ? 



In all these experiments it was deemed advisable to feed each box of flies 

 for two consecutive days on the monkey in order to make certain, if possible, 

 that each fly fed. For the same reason special attention was given to each 

 box of flies handled, with the result that it was found that flies reluctant 

 to feed in the morning would often, if given another opportunity some 

 hours later, bite with greater readiness. In spite, however, of all precautions, 

 it is impossible to be absolutely certain on this point. In the great majority 

 of cases the flies fed readily every clay. 



I. Does the Presence of Arsenic in the Bloocl imbibed clean an Infected Fly of 



its Flagellates ? 



To answer this query boxes of laboratory-bred G. palpalis, known 

 to be infective with T. gambiense, were placed upon monkeys which 

 had previously received a subcutaneous dose of arsenphenylglycin, - l grm. 

 per kilogramme body weight. The experiments were commenced 24 to 

 48 hours after the administration of the drug, and subsequently the 

 period of time was increased. No change in the flagellates was dis- 

 cernible if the interval between the giving of the arsenic and the feeding 

 exceeded 72 hours. The flies were dissected by Miss Robertson at 



c 2 



