MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 883 



over it to form the undulating membrane. The trypanosome moves by means 

 of the undulating membrane and flagellum and also through the contraction 

 of the myonemes which lie in the ectoplasm. In the blood, Trypanosoma 

 gambiense multiplies by binary division. It is not impossible that it may 

 multiply in other ways, as do other trypanosomes; for example, a trypanosome 

 of frogs loses its locomotory apparatus and forms a sphere, then the sphere 

 divides into many small spheres, each of which becomes a trypanosome. 

 Sometimes Trypanosoma gambiense loses its locomotory apparatus and forms 

 a sphere; these forms are found in the organs of infected animals. They are probably 

 more resistant, resting forms and a single trypanosome may be formed from some 

 of them. 



FIG. 1 86. Trypanosoma gambiense. (After Minchin, from Doflein.} 



i 



Trypanosomiasis is easily transmitted to susceptible animals by inoculation. It is 

 possible that the disease may be transmitted occasionally, in this way, by the mere 

 mechanical exchange of infected material, through an insect's bite, from an infected 

 to a healthy individual. But, as a rule, the disease can only be transmitted by the 

 bites of Glossina palpalis in which the organism has developed (Fig. 187); the 

 fly is not usually infective until three weeks after it has fed on an infected per- 

 son, and it retains its infecting power for some months. 



An incubation period of at least ten days intervenes between the 

 bite and the appearance of symptoms, but this period may be 

 much longer, for trypanosomiasis may manifest itself in apparently 

 healthy negroes several years after they have left localities in which 

 the disease could have been acquired. The disease sometimes causes 

 death within three or four months; but it may last for one or more 

 years. It is a chronic, wasting affection, characterized by loss of 

 strength and energy, and by an irregular fever. A change in the 

 mentality, red blotches on the skin, and enlargement of the lymphatic 

 glands, are all early signs of the disease. In the later stages, headache, 



