The Fly that Causes Sleeping-Sickness. 





In the year 1895 the Governor of Natal sent Surgeon-Major (now Colonel 

 Sir David) Bruce, of the Army Medical Service, into Zululand, in order that he might 

 investigate the tsetse-fly disease on the spot. Bruce made a number of painstaking 

 researches from which most of our present actual knowledge of the Insect has been 

 derived. He traced out the distribution of the disease, and made experiments 

 with the fly upon the native big game and domestic cattle. He found that before 

 feeding, the hind-body of the fly is so empty that the upper and lower walls appear 

 to be in contact, but after a few minutes the flv has imbibed so much blood that 

 the hind-body swells up to such an extent that its lower wall is transparent and 

 the colour of the imbibed blood shows through. 

 Bruce kept some of the flies in confinement until 

 all signs of their previous meal had disappeared 

 and the hind-body resumed its empty condition, 

 and fed them daily upon dogs for periods varying 

 from ten days to two months. The dogs remained 

 healthy, and showed that the mere bite of the 

 tsetse-flv was not capable of giving rise to the 

 disease. 



Then, in turn, the flies were fed upon dogs 

 known to be suftcring from nagana, and upon 

 healthy dogs, with the result that the latter 

 became affected by the disease. Many experi- 

 ments were made, but brieflv it ma^^ be said that, 

 in all cases where the flies were fed first upon 

 diseased and then upon healthy animals, the 

 blood of the latter vielded after a short interval 

 countless examples of a very low form of life ^ 

 which is always found in the blood of animals. 

 It appears to feed upon the red corpuscles of the 

 blood, producing a condition of anaemia, emacia- 

 tion, prostration, and finally, death. It is 

 carried from the sick to the healthy by the beak 

 of the fly. 



So far we have not mentioned sk'cping-sick- 

 ncss ; but the foregoing remarks u})on nagana 

 are a necessarx' introduction. At the end ol the 

 nineteenth century a disease called sleeping- 

 sickness began to s]:)read with alarming rapidity among human beings in Uganda, 

 and several \-essels homeward bound from F.ast .Africa were found to have 

 among their crews men suffering from this terrible maladw The disease 

 was proving a formidable barrier to the colonization of I'ganda, and the 

 seriousness of the matter was brought to the notice of the Royal Society. The 

 society appointed a commission of three medical men experienced in tropical diseases 

 to inquire into its nature and causes. Colonel Bruce was one of the three. His 

 previous researches into nagana suggested to him that this also might be a flv- 



1 Trvpanosonia brucci. 



Photo bv] 



[H. Bosliii. 



Hk.vd of Tsetsk-Fly. 



Tliis photograph on a large scale of the head ot the 

 fuscous tsetse-fly shows the apparatus by whose 

 use disease is propagaled. The hollow proboscis, 

 after insertion in the veins of a diseased beast or 

 afflieted man, carry some of the Rcrnis into the 

 system of a healthv victim. 



