484 • MITZMAIN. 



TRANSFERENCE OF FLIES TO IMMOBILIZED ANIMALS AFTER INFECTIVE FEEDING 



WAS COMPLETED. 



In this section consideration is given only to experiments 

 made in the attempt to transmit the infection mechanically. 

 Other experiments made under similar conditions, but in which 

 the primary aim was to demonstrate or eliminate a cyclical 

 development, are for the present omitted. 



By a "completed" feeding is meant a condition in which the 

 parasite has, to all appearances, satiated its craving for blood. 

 As will be shown later in the discussion of feeding habits of 

 this insect, a fly of this species does not ordinarily feed more 

 than once in six to eight hours. However, there are tabulated 

 several instances in which feeding recurred within twenty 

 minutes or less. The feeding is, therefore, considered as "com- 

 plete" when the fly has not been experimentally disturbed or 

 restricted. 



The conditions of these experiments are highly artificial, let 

 it be recalled, and this despite every conscientious effort to simu- 

 late natural environments. Under the conditions provided, full 

 freedom of their biting was permitted, and their flight was 

 restricted within the limits of the animal cage, a maximum range, 

 in one series of experiments, of not less than 10 meters. 



Reference is made to the results of completed feeding of this 

 fly in experiments recorded by several workers : 



Nabarro and Greig,(30) working with Stomoxys and trypanosomiasis in 

 Uganda, failed to transmit cattle trypanosomes when the intervals between 

 biting were as long as six to twenty-four hours. 



Bouffard,(3i) working with souma in French Sudan, succeeded in trans- 

 mitting Tr. cazalboui by Stomoxys. The experimental transmission was 

 direct in conveying the disease from an infected to a noninfected calf kept 

 in the same stable for two days. Forty Stomoxys were used. Here inter- 

 rupted feeding probably influenced the results. 



Martini, (32) in trypanosome experiments and observations with dogs and 

 horses in Berlin, records negative results. S. calcitrans was the fly used. 

 Presumably no interrupted feeding was attempted. 



Greig and Gray, (33) finding that they could not convey mule and cattle 

 trypanosomes of Uganda by the bites of Stomoxys after intervals of eight 

 to twenty-four hours, considered it proved that Stomoxys could not convey 

 trypanosomes. Interrupted feeding was not attempted, although tsetse 

 flies could transmit these trypanosomes by the direct method. 



In the following table are outlined the data of the experi- 

 ments under discussion. The four infected animals used in each 

 instance contained trypanosomes in varying numbers at the 



