562 Sleeping Sickness 



the trypanosomes, but there is no doubt about the chief 

 agent being Glossina palpalis. With increased entomologic 

 and geographic information it has been found that there 

 are certain districts where these flies abound though the dis- 

 ease is unknown, but that only shows that in those districts 

 the flies are not infected. Tsetse-flies are not, as was for- 

 merly supposed, peculiar to Africa, but have been found in 

 Arabia, where African lethargy could no doubt spread should 

 the flies become infected through imported cases of the dis- 

 ease. The inability of the disease to spread in England and 

 America depends upon the absence of tsetse-flies from those 

 countries. 



According to recent experiments of Bruce, Harrison, Hamer- 

 ton, Batement, and Mackie, and especially of Kleine, only a 

 small proportion of the tsetse-flies are capable of spreading 

 the infection, because the transmission is not merely the 

 mechanical transplantation of the trypanosomes, but the 

 implantation of the parasites after they have completed a 

 certain developmental cycle in the body of the fly. Thus, 

 the insect does not become infective until about eighteen 

 hours after infecting itself, and remains infective seventy- 

 five days (Brumpt). Of course, to be infected, one must be 

 bitten by a fly itself infected and in the infective stage. 



It is possible for the disease tb be transmitted from human 

 being to human being through such personal contacts as may 

 afford opportunity for interchange of blood. Thus, Koch 

 observed that in certain parts of Africa where there were no 

 tsetse-flies the wives of men that had become infected in 

 tsetse-fly countries sometimes developed the disease, prob- 

 ably through sexual intercourse, a probable explanation when 

 one remembers that it is solely or chiefly by such means that 

 a trypanosome disease of horses Dourine or Maladie du 

 coit, caused by Trypanosoma equiperdum is transmitted. 



Transmission to Lower Animals. Try panosoma gambiense 

 is infectious for monkeys as well as for human beings. In the 

 monkeys a disease indistinguishable from the sleeping sickness 

 is brought about. It is also infective for dogs, cats, guinea- 

 pigs, rabbits, rats, mice, marmots, hedgehogs, goats, sheep, 

 cattle, horses, and asses. The lower animals are not, how- 

 ever, so far as is known, subject to natural infection. 



Pathogenesis. The first effect of human trypanosomiasis 

 seems to be fever of an irregular and atypical type, occurring 

 in irregular paroxysms. It was in such cases that Forde and 



