402 



SPECIFIC MICRO-ORGANISMS 



trypanosomes multiply in the digestive tract of these insects, 

 producing various forms, many of them resembling herpetomonas 

 and leptomoiias. Fleas remain infective for a long time. 



Cultures of Tr. lewisi vfere obtained by MacNeal and Novy^ 

 in 1902-03, in the condensation fluid of inclined blood-agar, and' 

 the infection was reproduced by inoculation of these cultures. 



Fig. 160. — Trypanosoma lewisi. Eight-cell rosette in division. Note the long 

 original or parent whip on one of the cells. Several cells show a second flagellum 

 growing out preparatory to a further division. X 2250. (After MacNeal.) 



The size and shape of the organism in culture is quite variable. 

 The actively dividing forms are usually grouped in rosettes with 

 flagella directed centrally, and the cells themselves are pear- 

 shaped or oval. Herpotomonad forms are common. 



The infection with Tr. lewisi rarely results in death of the rat. 



' Contributions to Medical Research, dedicated to Victor Clarence Vaughan, 

 1903, pp. S49-S77- 



