494 MITZMAIN. 



moderate to numerous. The animal died August 12, 1912, when 

 its heart's blood was used to test the disease susceptibilities of 

 the 2 horses, 275 and 279, used in a previous experiment. Trypa- 

 nosomes in moderate numbers were recovered from these 

 animals August 17, 1912. 



DURATION OF THE INFECTION IN THE PROBOSCIS OF STOMOXYS. 



Button, Todd, and Hanington(34) found that red cells and Tr. gam- 

 biense were almost always present in the labium of Gl. palpalis up to ten 

 minutes after feeding. The longest period in which trypanosomes were 

 found in the labium was one and three-fourth hours, and red cells seven 

 and one-half hours. 



As far as can be determined no authentic records exist in 

 which Stomoxys has been investigated in this connertion. 



An effort was made to determine how long the proboscis of 

 Stomoxys can retain trypanosomes. Six experiments were per- 

 formed with 2 animal inoculations in each. The method em- 

 ployed was to feed laboratory-bred flies on an infected guinea pig 

 and after certain intervals stupefy the insects and immediately 

 sever the head from the body. With another set of instruments 

 the proboscis was dissected and at once emulsified with normal 

 saline solution and injected on a cotton pledget into a subcuta- 

 neous pocket of the abdomen of a guinea pig previously etherized. 

 This was followed by a similar mode of inoculation, using dis- 

 infected instruments, with the macerated abdomens. The thorax 

 was invariably discarded. The interval of time between the 

 withdrawal of the insect's labium from the infected animal and 

 the dissection of the mouth parts was carefully noted. 



In two experiments the flies were purposely interrupted in 

 the biting process, and in the other trial the flies were allowed 

 to complete the meal unmolested. In the cases of interrupted 

 feeding one-half to three minutes were allowed for each fly to 

 insert the proboscis to the depth of the bulb of the labium, the 

 feeding being interrupted at a stage when there ensued a barely 

 perceptible inflation of the abdomen. 



When permitted to feed uninterruptedly it has been noticed 

 that this insect sucks its food cleanly, no residue adhering to the 

 labellum of the mouth or to the labium externally. In one in- 

 stance (experiment 5) it was observed that in 2 flies chloroformed 

 prior to dissection droplets of fresh blood oozed from the pro- 

 boscis. The abdomens of these flies were fairly engorged with 

 blood. It is suggested that the phenomenon observed was a 

 regurgitation of blood from the pharynx into the labium, result- 

 ing either from the engorgement of the stomach or from the 



