A CHAPTER ON INSECTS 141 



sleeping sickness, Bruce had the help of many native 

 collectors who were paid to bring to his camp the 

 various flies and other insects of the district. Finally, 

 the source of transmission was fastened on a par- 

 ticular species of the tsetse-fly Glossina palpalis. 

 The tsetse-flies are a genus of flies only found in 

 Africa. There are seven species known the par- 

 ticular fly that transmits sleeping sickness in human 

 beings is a little bigger than the common house fly 

 and much like it in color. 



To establish an undoubted connection between 

 the tsetse-fly and the transmission of sleeping sick- 

 ness came to Bruce as a triumph of scientific observa- 

 tion and deduction. Finding that monkeys also were 

 susceptible to the disease he caused infected flies to 

 bite monkeys, thus producing the disease and dem- 

 onstrating the mode of its transmission. 



In 1906, a sort of arsenic aniline (Atoxyl) was 

 found by Thomas and Breinl to be helpful in some 

 cases. The suggestion of this substance as a possible 

 remedy was erroneously ascribed to Robert Koch 

 who merely confirmed the observations of the earlier 

 investigators. 



To avoid a common confusion it may be well at 

 this point to emphasize the fact that the three 



