488 MITZMAIN. 



MECHANICAL TRANSMISSION BY INTERRUPTED FEEDING. 



In this series of experiments I offer no apology for the unusual 

 number of repetitions made to arrive at a conclusion. Scru- 

 pulous care has been taken for the details of experimental pro- 

 cedure. Numerous assertions are made by writers that positive 

 results are infallible when a few flies are transferred while 

 feeding on a surra host to an experimental animal. The careful 

 observers are more cautious, and present more accurate and 

 specific data : 



Button, Todd, and Hanington<84) state: "The experiments of all ob- 

 servers show that it is frequently necessary to feed hundreds, almost 

 thousands, of flies on a susceptible animal before it becomes infected. In 

 this regard fewer flies are, of course, needed when there is practically no 

 interval between the feeds." 



Austen (35) summarizes that from the evidence compiled Stotnoxys can 

 convey trypanosomes directly from an infected to a healthy animal when 

 the bites follow one another immediately, and, when the interval between 

 the bites is longer, although active trypanosomes may be present in the 

 intestine of the fly, its bite is innocuous. 



Schuberg and Kuhn(36) transmitted Tr. brucei and Tr. gamhiense in 

 interrupted feeding by the bite of Stomoxys calcitrans. Eight and 13 

 flies were used in two experiments with Tr. brucei, and 9 and 8 flies 

 in two experiments with Tr. gambiense. One positive result was obtained 

 with feeding after a ten-minute interval. 



Schuberg and Kuhn(37) give an account of various attempts in Hamburg 

 to transmit by means of Stomoxys the diseases of nagana, dourine, sleep- 

 ing sickness, and rat trypanosomiasis. Rats and mice were used in inter- 

 rupted feedings. Positive results were obtained in all cases except in 

 the attempt to convey the rat trypanosomes. 



Sergent, Ed. and fit., (38) investigating the method of transmission of 

 Tr. soudanense, the cause of debab, a camel disease, obtained one positive 

 result with Stomoxys in 14 feeding experiments by the interrupted method. 



Minchin, Gray, and Tulloch(39) obtained 1 positive result in 4 experi- 

 ments with the "Jinja" cattle disease of Uganda by using Stomoxys, 

 while by using Gl. palpalis 4 out of 5 results were positive. These 

 were experiments in direct transmission with no interval between bites 

 of the flies. 



Martin, Leboeuf, and Roubaud(8) show that Tr. brucei can be conveyed 

 mechanically by Stomoxys. In the positive experiment 3 flies were used 

 to convey infected blood to a healthy kitten after intervals of thirty 

 seconds to one and one-half minutes. In a similar experiment a negative 

 result was obtained with 3 flies on a healthy guinea pig at intervals of ten 

 and fifteen minutes. 



In Table V the data show the feeding of flies on monkeys. 

 Here are tabulated 14 experiments with 10 animals, 4 of these 

 being used a second time at the expiration of three to four weeks. 



