100 



TRYPANOSOMES AND SLEEPING SICKNESS 



they attach themselves by their flagella (Fig. 21D) and, rapidly 

 multiplying, undergo a crithidial stage. As multipUcation con- 

 tinues free-swimming trj'-panosome forms are again produced 



To cerebrospinal fluid causing sleeping 

 sickness and death. 



Transmission by 

 bite of tsetse fjy. 



^ Man. Antelope, etc. 



Trypanosomea 



in human blood causing 

 Trypanosome fever. 



iransm i53ion by bite 

 of tsetse fly. 



Tsetse Fly 



Forms in salivary glands 

 ready for re. Infection. 

 '^(20"--50"- day) 



Crithidial forms in 



salivacy glands 

 (2 or >3 daya later) 



Forms in midgut,(VSf 

 after infective meal). 



newly arrived form i 

 .saliva ry aland. 

 (I2'*to20'|'dgyd.) 



Long slender forms In proventriculas. 

 (about I0<''tol5"'day5) 



Fig. 21. Life History of Trypanosoma gambiense. X 1500. (Constructed 

 from figures by Miss Robertson.) 



which very closely resemble the i)arasitcs in vertebrate blood 

 (Fig. 21 E) and which are now capable of infecting a vertebrate 

 host. The whole cycle in the fly usually occupies from 20 to 30 

 days. According to Kinghorn and Yorke the time required for 



