284 Messrs. Minchin and Thomson. Transmission of [Jan. 7^ 



III. Conclusions to he drawn from the Experiments, 



(1) The rat-flea Ccratoj^hyllus fasciatus can transmit Trypanosoma lewisi 

 from infected to non-infected rats. 



(2) The transmission takes place by the cyclical method. 



(3) Transmission by the direct method has not been proved to occur. 



(4) The incubation-period of the flea, that is to say the period occupied by 

 the developmental cycle of the trypanosonie, has a minimum length of six or 

 seven days, but may be longer. 



(5) The multiplication-period of the trypanosome in the rat has a length 

 of about 12 days. 



(6) In the developmental cycle the establishment of the trypanosome in the 

 flea begins with multiplication of Crithidia-like forms in the rectum. 



Our conclusions with regard to the method of infection by the invertebrate 

 host agree in the main with the results of Kleine's investigations upon the 

 transmission of Sleeping Sickness of man, and Tsetse-fly Disease of animals, 

 by Glossina palpalis and G. morsitans respectively. 



Postscript. — January 24, 1910. Tabular Summaries of Experiments C, D, and E. 



Experiment C. 



Cage C colonised with 160 fleas that had been exposed to infection from November 24 



till November 27. 



Rat. 



Put in. 



Tiiken out. 



Eesult. 



Trypanosomes 

 first seen. 



Multiplication 

 ended. 



CI 



November 27 



November 30 



0 







C2 



30 



Deoonibcr 3 



+ 



December 10 



December 15 



C3 



December 3 



•> 



+ 



]3 



18 



C4 



6 



8 





13 



19 



C5 



8 



10 



+ 



14 



21 



C6 



10 



n 



+ 



15 



23 



C7 



„ 11 



13 





17 



24 



C8 



13 



15 



+ 



20 



26 



C9 



15 



17 



+ 



21 



Found dead on 













Dccondicr 28 



C 10 



17 



20 



+ 



26 



December 30 



C 1 1 



20 



22 



+ ■ 



28 



January 1 



C 12 



22 



24 



Found dead on December 2( 



C 13 , , 



24 



28 



+ 



January 3 



8 



C 14 



28 



31 



0 







C 15 



31 



.IiiMimrv 3 



+ ■ 



.Iiiiumry 8 



Jiinuarv 13 



V 10 



Janimrv 3 

 >. * 





+ 



10 



„ ■ 15 



C 17 



■ 10 



+ 



12 



17 



C 18 



10 



13 



+ 



„ 19 



24 



I 



