ROLE OF STOMOXYS CALCITRANS. 



507 



The following table shows the length of time during which 

 Stomoxys was found to harbor the surra organisms. The few 

 laboratory-bred flies that could be spared for the purpose were 

 fed on a virulent strain of guinea-pig surra and injected into 

 healthy guinea pigs at stated intervals. When the fly was to be 

 kept beyond twenty-four hours, it was fed a few minutes each 

 day on an animal not included in this experiment. In every case 

 the entire fly was inoculated. 



Table XIII. — Results of inoculating flies fed on an infected host. 



Minutes jDays. hrs. 



3 ! (") 



Length 

 of time 



of in- 

 fective 



meal. 



Time elaps- 

 ing after 



feeding on 



infected 



host. 



Num- 

 ber of 



flies 



in- 

 jected. 



18 

 18 

 24 

 24 

 30 

 48 

 54 



29 00 

 68 00 



Trypanosomas 

 present or absent 

 at the time of injec- 

 tion. 



Present 



do 



Few alive _ 

 Few active 



Absent 



do 



do 



do 



do 



do 



do 



No. of 



the 



test 



guinea 



pig 



used 



37 



50 

 168 

 91 

 32 

 93 

 130 

 126 

 73 

 74 

 34 



Results of inoculation. 



Positive on eighth day. 

 Positive on thirty-eighth 



day at death. 

 Positive on sixth day. 

 Positive on forty-second 



day at death. 

 Animal negative. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 

 Do.b 



" Used immediately. 



^ A wild fly used for successive feedings on guinea pigs. 



A check on the experiment in the use of this species of fly is 

 offered in a former experiment by an inoculation of a forty-two- 

 hour infected mosquito, Stegomyia fasciata. Here a positive 

 result was obtained. 



THE QUESTION OF HEREDITARY TRANSMISSION. 



The experiments next described were performed with the pur- 

 pose of eliminating all possible avenues through which infection 

 might possibly be transmitted by means of the fly. 



Sergent, Ed. & £;t. (38) recount experiments with Algerian trypanoso- 

 miasis in which feeding tests, with young ticks hatched from eggs laid by 

 adults removed from heavily infected animals, were negative. 



Button, Todd, and Hanington(34) write: "It is possible that the progeny 



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