390 



TR YPA NO SO MI DM 



D. Salivary Gland Infection.— Accoiding to Bruce and his col- 

 laborators, if G. palpalis is fed with T. castellanii, the proboscis is 

 not involved in the further development. The % now becomes 

 non-infective for some twenty-eight days on an average. The 

 trypanosomes in five to seven days disappear (possibly become intra- 

 cellular), but later return in a small percentage of flies, and multiply 

 in the fore, mid, and hind guts, generally as long, moderately broad 

 forms, with protoplasm which stains well, and contains an oval 

 central nucleus, a small micronucleus, undulating membrane, and a 

 fiagellum with a blepharoplast. After twenty-eight days it is found 

 that the salivary glands becom^e infected with the short, stumpy 

 forms already mentioned above, and now the fly is found to be 

 infective and to remain so for long periods. These short stumpy 

 forms have been noted by Kleine in the intestine. Miss Robertson 

 finds that the trypanosomes infect the salivary glands from the gut 

 via the proboscis and the salivary ducts. 



1 2 3 



Fig, 92. — Djevelopment of T. castellanii Kruse, 1903. 

 I, In the vertebrate blood; 2 and 3, in the mid-gut; 4 and 5, in the 

 hind-gut; 6, in the salivary glands of the tsetse-fly. 

 (After Bruce, Hamerton, Bateman, and Mackie.) 



Kinghorn and Yorke have shown that the salivary glands of 

 Glossina morsitans become infected in a somewhat similar manner 

 with T. rhodesiense. 



Chagas has seen trypanosomes in the body cavity and salivary 

 glands of Lamus megistus, which are without doubt the forms 

 which are inoculated in infections. 



E. Rectal Encystment.~M.mchin finds that the crithidial forms of 

 T. grayi become encysted in the rectum of G. -palpalis. 



F. Ovum Infection. — This has not been proved to take place. 

 Conditions Influencing Development.— Kinghorn and Yorke have 



shown that the development of T. rhodesiense in G. morsitans is 

 markedly influenced by the temperature of the air, 75° to 85° F. 

 being more favourable than 60° to 70° F., and, under favourable 

 conditions, the first stage of development can take place, but not the 

 later stages, and flies may remain with the parasites incompletely 



