24 



Dr. H. L. Duke. Experiments with 



[Sept. 28, 



Expt. 567. — Positive Box of G. palpalis. 



Date. 



Procedure. 



Remarks. 



Jan. 20—21 



Fed on Monkey 620 48—72 hours after 



administration of arsenpbenylglycin, 



22—26 

 27 .... 



'1 grm. per kilogramme. 

 Starved. 



Dissected 



1 + fly found. 



Description of the positive fly : — 

 Hindgut : Nil. 



Posterior part of thoracic gut : Normal, + + + . 

 Anterior fart of thoracic gut : Nil. 

 Proventricidus : Nil. 

 Salivary gland : + + + , normal. 



From the above experiments it will be seen that the flagellates in the gut 

 of flies fed upon a monkey within 24 to 48 hours of the administration of 

 arsenphenylglycin in doses of 01 grm. per kilogramme are markedly 

 affected. The flagellates in the salivary glands are apparently not injured 

 in any way, nor does the fly lose its power of infecting. This evidence 

 supports the theory that the salivary gland flagellates are the normal 

 infecting agents. In a paper shortly to be published, Miss Eobertson brings 

 forward a further mass of evidence to support this conclusion. There is 

 no reason to doubt that the secretion of the salivary gland is poured out 

 into the wound made by the fly's proboscis at the commencement of the 

 act of feeding. Whether or not this process is repeated during the course 

 of feeding cannot well be determined. These functions of the salivary gland 

 and its contained flagellates are well borne out by the interrupted feeding 

 experiment to be referred to shortly. 



It is plain that any attempt to clean a positive fly of its flagellates by 

 feeding it upon an animal whose blood contains arsenic will fail, as the 

 gland flagellates will not come into contact with the drug. 



II. Has the Preliminary Feeding of Flies on Arsenic-containing Blood any 

 Effect on the Subsequent Development of the Flagellates in their Interior ? 



The first pair of experiments, Nos. 336 and 337, devised to elucidate this 

 point proved fruitless, as no positive flies were found either in the arsenic box 

 or its control. 



