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MiNCHiN (E. A.) & Thomson (J. D.). The Rat-Trypanosome, Trypano- 

 soma lewisi, in its Relation to the Rat-Flea, Ceratophyllus fasciatus. 

 —Qtrly. Jl. Micro. Sci., London, Ix, pt. 4, January 1915, pp. 463- 

 692, 10 plates, 24 figs., 13 tables. 



A detailed account is given of investigations which have been 

 carried on during the last five years on T. lewisi and its relation to 

 C. fasciatus. The first part of the memoir describes the technique of 

 the experiments and gives details of the anatomy and histology of the 

 flea. The second part deals with the development of T. lewisi in the 

 flea ; the trypanosome is confined throughout its development to 

 the digestive tract, where it passes through various phases, some of 

 which are intracellular in the epithelium of the stomach. No experi- 

 mental proof of sexual phases was obtained. The third part deals 

 with the problems of transmission and development of T. lewisi. 



The following propositions have been experimentally established, 

 details of the experimental evidence being given in each case : — • 

 (1) T. lewisi is transmitted from rat to rat by the rat flea, C. 

 fasciatus ; (2) transmission takes place by the cycHcal method 

 and has not been proved to occur by the direct method ; (3) trypano- 

 somes appear in the blood of the rat from five to seven days after 

 infection and this multiplication in the blood of the rat comes to 

 an end 11 to 13 days after infection ; (4) the cycle of development 

 in the flea requires a minimum of five days for its completion ; 

 (5) transmission is never effected until the developmental cycle 

 is completed, i.e., until at least five days have elapsed since the 

 first exposure of the fleas to infection ; (6) infection of the rat is- 

 brought about by the small trypanosome-form which is the final 

 form of the development ; (7) the final infective form of the cycle 

 is developed first in the rectum on the fifth day of the develop- 

 mental cycle, but may appear later in the stomach ; (8) the develop- 

 mental forms of the trypanosomes in the flea are not infective when 

 inoculated into the rat during a period extending from a short time 

 (^ hour ?) after being taken up by the flea until the developmental 

 cycle is complete ; (9) the flea, once it has become infective, remains 

 80 for a considerable time; (10) the trypanosome does not penetrate 

 into the salivary glands of the flea, but is confined during its whole 

 development to the digestive tract; (11) the rat can become infected 

 by eating infected fleas, but not until the developmental cycle of the 

 trypanosome in the flea is completed ; (12) infection of the rat is 

 effected contaminatively, by way of the rat's mouth, by the rat licking 

 from its fur or skin the moist faeces of infective fleas containing the 

 final propagative form of the cycle ; (13) hereditary transmission 

 of the trypanosome from flea to flea does not take place ; (14) the 

 trypanosomes in the blood of the rat render fleas infective very soon 

 after they make their first appearance in the blood, before their malti- 

 plication period is over. 



Experiments failed to prove whether the flea can infect the rat 

 by inoculating the trypanosomes into it through the proboscis. 

 The following conclusions are also given : (1) the trypanosornes- 

 succeed in estabHshing themselves in the flea and rendering it infective 

 to the rat in only a small proportion of the individuals that ingest 

 them; (2) starvation of the flea during the incubation period of 



