278 Messrs. Minchin and Thomson, Transmission of [Jan. 7, 



rectum and in one of the Malpighian tubes. A healthy, non-infected tame rat 

 (B 2) was put into Cage B. 



Bat Bl was examined regularly from 23 10/09 till 8/11/09; no trypauo- 

 somes were fovmd at any time in its blood. 

 8/11/09. — Eat B 2 examined, many ti-ypanosomes found in its blood; all adult forms, 

 apparently just past the multiplication -period. 



Tabular Summary of Experiment B. 



Cage B colonised with 157 fleas that had been exposed to infection from October 11 



till October 15. 



Eat. 



Put in. 



Taken out. 





Bl 



October 15 

 „ 19 



October 19 

 Left ill 





B2 





Having confirmed conclusions that fleas are capable of transferring 

 T. lewisi from infected to clean, healthy rats, and having shown that 

 infection did not take place by the direct method. Experiments A and B 

 were prolonged in order to ascertain- whether fleas once infective retain 

 infection so as to be capable of infecting a series of clean, healthy rats. 

 In both cases it was found that fleas once infective do so retain the 

 infection, and can infect a series of rats without themselves being exposed to 

 fresh infection, but as this point is so clearly brought out in Experiment C 

 which follows, the detailed accounts of the prolongations of Experiments A 

 and B have not l)een added. 



Experiment C. 



24/11/09. — 20() rieas taken from the breeding cage were put into the special tin cage 

 together with a heavily-infected tame rat, showing many trypanosomes in it 

 blood. This rat had been subnntted to chloroform-vapour immediately before 

 and carefully searched to ensure that it harboured no fleas. 

 27/11/09. — 160 fleas recovered from the above cage were put into a freshly prepared, 

 flea-proof cage (Cage C), together with a healthy, clean tame rat (Eat C 1). 

 5 fleas were di.ssected, and in all try])auosomes were found. In the rectum of 

 1 flea (?) large masses of multiplying (.'rithidia-like forms were found. In the 

 rectum of another flea ((?) multii)lyiug clumps were also found. 

 30/11/09. — Eat C 1 was removed from Cage C, was carefully freed from Hea.s by the aid of 

 chloroform-vapour, nnd was ])ut into a separate flea-proof cage by itself. A 

 healthy, clean tame rat (C 2) was put into Cage C. 



Eat CI was examined regularly from 1/12/(19 until :!/l/I0. No tryjiano- 

 somes were foinid in its blood at any time. 

 3/12/09.— Kat C2 was removed from Cage C, was carefully freed from fleas, and was 

 tlien l)iit into a separate freshly-])re])ared tlea-jn-oof <age by itself. 11 fleas 

 recovered from it were put back into Cage C. A healthy, eleau tame rat 

 (Kat C 3) was then ])ut into Cage C. 



J{at C2 was cxaiiiined daily from 4/12/09, and on 10/12/09 trypanosomes 



