37 



place. They emerge as flies five or six weeks later. Before 

 feeding, the abdomen of the fly is so empty that the upper 

 and lower walls appear to be in contact, but after a few 

 minutes the fly has imbibed so much blood that the abdomen 

 has swollen to such an extent that its lower walls are trans- 

 parent and the colour of the blood shows through. Unlike 

 the Clegg, both sexes of the Tsetse-fly indulge in the blood- 

 sucking habit. Bruce kept some of these flies in captivity 

 for some days, until their previous meal had become entirely 

 assimilated and the abdomen resumed its empty condition, 

 and then fed them daily upon dogs for periods varying from 

 ten days to two months. The dogs remained healthy, and 

 thus showed that the mere bite of the Tsetse-fly was not 

 capable of giving rise to the disease. 



Then the flies were fed in turn upon dogs known to be 

 suffering from Nagana and healthy dogs, with the result that 

 these latter became affected by the disease. Many experi- 

 ments were made, but briefly it may be said, that in all cases 

 where the flies were fed first on diseased and then upon 

 healthy animals, the blood of the latter yielded after a short 

 interval countless examples of a Hasmatozoon, now known as 

 Trypanosoma brncei. This Hasmatozoon appears to feed upon 

 the red corpuscles of the blood, producing a condition of 

 an^tmia, emaciation, prostration, and finally death. 



So much for Nagana. In more recent years a disease 

 called Sleeping Sickness began to spread with alarming 

 rapidity among human beings in Uganda, and several vessels 

 homeward bound from East Africa were found to have 

 among their crews men suffering from this terrible com- 

 plaint. Last year the Royal Society appointed a commission 

 to inquire into this disease, which was promising to prove a 

 serious bar to the colonisation of Uganda. The commission 

 consisted of Surgeon-Major (now Colonel) Bruce, Dr. 

 Nabarro, and Captain Greig, of the Indian Medical Service. 

 The report of that commission has now been published, and 

 forms most interesting reading. From certain facts com- 

 municated to him by the doctor in charge of the hospital, 

 who had detected Trypanosomes in the blood of the patients. 

 Colonel Bruce got the idea that they might owe their 

 presence to the attacks of Tsetse-flies, and he directed his 

 inquiries to test this. As the results of his experiments and 

 researches, described in detail in the report, we may regard 

 it as being now established that the Sleeping Sickness is a 

 human Tsetse-fly disease, and is caused by the activity of a 

 Haematozoon {Trypanosoma gambicnse, Dalton) in the blood 



