1910.] 



Trypanosoma lewisi by the Rat-Jlea. 



277 



6 other fleas recovered from the tin cage were dissected ; in 5 of them trypano- 

 somes were found, and in one instance multiplying forms were seen in the 

 rectum. (The recta of the others were not specially examined.) 

 12/10/09. — Rat A 1 was removed from Cage A, was carefully cleaned from fleas by the 

 aid of chloi-oform-vapour, and was put into a separate cage by itself ; two 

 fleas removed from it were dissected. A healthy, clean tame rat (Rat A 2) was 

 then put into Cage A. 



Rat Al was examined regularly from 16/10/09 to 13/11/09, but no trypano- 

 somes were found. On 15/11/09 Rat A 1 was found dead; no trypanosomes 

 were found in its blood. 



On 26/10/09 Rat A 2 was found dead; no ti-ypanosomes were found in its 

 blood. 



27/10/09. — A healthy, non-infected tame rat (Rat A 3) was put into Cage A, whence the 

 dead Rat A 2 had been removed the day before. 



6/11/09. — Rat A3 examined, no trypanosomes found. 



8/11/09.— „ 

 10/11/09.- „ 



11/11/09. — Rat A 3 examined, trypanosomes found; a smear made showed multiplying 

 forms. 



13/11/09. — A smear made from the blood of Rat A3 showed trypanosomes abundant, 



still multiplying forms. 

 15/11/09. — A smear of the blood of Rat A3 showed very few multiplying forms. 

 16/11/09. — ^A smear from Rat A3 showed the trypanosomes all of the adult form ; 



multiplication ended. 



Tabular Summary of Experiment A. 



Cage A colonised with 44 fleas that had been exposed to infection from October 4 till 



October 8. 



Eat. 



Put in. 



Taken out. 



Result. 



Trypanosomes 

 first seen. 



Multiplication 

 ended. 



Al 



A2 



A3 



October 8 

 12 



» 27 



October 12 0 — | — 

 Found dead, Cage A, on October 26 ; no trypanosomes seen 

 in its blood. 



Left in j + j November 11 j November 16 



Experiment B. 



11/10/09. — 200 fleas taken from the breeding cage were put into the .special tin cage 

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

 blood (the same rat that was used in Experiment A). 



15/10/09.— 157 fleas recovered from the above cage were put into a freshly-prepared, 

 flea-proof cage (Cage B), together with a healthy, non-infected tame rat 

 (Rat B 1). Two fleas were dissected, multiplying forms of trypanosomes were 

 foimd in the rectum of one. 



19/10/09. — Rat B 1 was removed from Cage B, was carefully freed from fleas by the aid 

 of chloroform- vapour, and was put into a separate cage by itself. Of 26 fleas 

 removed from Rat B 1, 21 were put back into Cage B, and the other 5 were 

 dissected ; in one of the fleas dissected multiplying forms of trypanosomes were 

 found in the rectum, and in another multiplying forms were found in the 



