MASTIGOPHORA 



191 



Trypanosomiasis. The next flagellate to cause disease is 

 the Trypanosoma, two species of which are pathogenic for 

 man, causing a disease called trypanosomiasis, or sleeping 

 sickness. This affection is commonest in Africa, because of 

 the prevalence of the tsetse fly, in whose body the protozoa 

 are transmitted. The bite of these flies becomes infective for 

 the well three days after biting the affected, and continues 

 so for about four or five weeks. These pests bite during the 



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FIG. 60. Protozoa in a case of tropical ulcer. 

 (After Wright.) 



X 1500 approximately. 



daytime, so that protection and screening of houses is insuf- 

 ficient usually to guard against disease. Inasmuch as it is 

 thought that some species of trypanosomas in the blood of 

 the lower animals are infective for man, strict quarantine is 

 placed on animals within countries where this disease exists, 

 and upon exported specimens. 



When the protozoa come into the blood they are carried 

 throughout the body and lodge chiefly in the lymph glands, 



