SLEEPING SICKNESS 663 



trypanosome of sleeping sickness after eight to twenty-four 

 hours. 



Further evidence has been collected, which shows : 



1. That sleeping sickness is at first a polyadenitis caused by 

 the Trypanosoma gambiense. 



2. That, in addition to enlargement of the glands, the blood 

 shows a constant lymphocytosis at all stages of the disease. 



3. That sleeping sickness itself is the last stage of the 

 disease, and is always fatal. It consists in a polyadenitis, 

 together with signs and symptoms of changes in the nervous 

 system, and the onset of these symptoms coincides with the 

 entrance of the trypanosoma into the lymph spaces of the ner- 

 vous system, accompanied by an increase of the mononuclear 

 elements of the cerebro-spinal fluid. 



4. That the resistance both of men and monkeys to the 

 Trypanosoma gambiense varies greatly in different cases, and that, 

 apparently, a certain number of both acquire sufficient immunity 

 to arrest the development of the disease at the early stage. 



5. That the action of arsenic on the disease is only partial. 

 It destroys a number of trypanosomes, and these probably act 

 as immunising agents. In the polyadenitis, arsenic increases 

 the natural resistance. 



6. That bacterial invasion, mainly by cocci, occurs in some 

 cases, but only at the very last. 



7. That, in addition to the Trypanosoma gambiense, other 

 trypanosomes occur in Uganda, probably pathogenic to 

 animals. 



8. That these other trypanosomes differ widely from 

 Trypanosoma gambiense. 



9. That one of these trypanosomes is probably identical 

 with Trypanosoma Brucei. 



10. That these different trypanosomes are conveyed from 

 the sick to the healthy by the Uganda tsetse fly {Glossina 

 palpalis) and other species of Glossina. 



In Uganda at the present time, in the sleeping sickness 

 areas, from 50 to 75 per cent, of the inhabitants have poly- 

 adenitis, but are capable of doing their ordinary work, and 

 have few symptoms ; these individuals act as reservoirs for 

 the trypanosome. 



According to their after-history, these cases may be divided 

 into two classes : 



