1910.] 



Tiypanosoma lewisi hy the Rat-jiea. 



281 



Rat D2 was examined regularly from 16/12/09 until 22/1/10. No trypano- 

 sonies were found at any time in its blood. 

 14/12/09.— A healthy, clean tame rat (Rat 1)3) was put into Cage D. 



15/12/09. — Rat D 3 was removed from Cage D, was carefully freed from fleas, and was 

 then put into a freshly-prepared flea-proof cage by itself. .36 or 38 fleas 

 recovered from Rat D 3 were returned to Cage D. 



Rat D 3 was examined regularly from 17/12/09 until 21/12/09, when 

 trypanosonies were first seen in its blood. Permanent smears were then made- 

 of its blood from 21/12/09 till 26/12/09, when it was found dead before the 

 multiplication-period had come to an end. 

 16/12/09. — A healthy, clean tame rat (D4) was put into Cage D. 



17/12/09. — Riit D4 was removed from Cage D, was carefully freed from fleas, and was 

 then put into a freshly-prepared cage by itself. 15 fleas were recovered from 

 Rat D 4, but were all accidentally killed. 



Rat D 4 was examined regularly from 20/12/09 till 22/1/10. No try pan q- 

 somes were found at any time in its blood. 



18/12/09. — A healthy, clean tame rat (Rat D5) was put into Cage D. 



20/12/09. — Rat D 5 was removed from Cage D. Though carefully searched by the aid of 

 chloroform-vapour, no fleas were found on it. Rat D 5 was put into a freshly- 

 prepai-ed cage by itself. A healthy, clean tame rat (Rat D 6) was then put into 

 Cage D. 



Rat D 5 was examined regularly from 21/12/09 till 22/1/10. No trypano- 

 sonies were found at any time in its blood. > 

 22/12/09. — Rat D6 was removed from Cage D, was carefully freed from fleas, and was 

 then put into a separate fi-eshly-prepared cage by itself. 4 fleas recovered from 

 Rat D 6 were returned to Cage D. A clean, healthy tame rat (Rat D 7) was 

 then put into Cage D. 



Rat D 6 was regularly examined from 23/12/09 till 22/1/10. No trypano- 

 somes were found at any time in its blood. 

 24/12/09. — Rat D 7 was removed from Cage D. Though carefully searched by aid of 

 chloi-oform-vapom-, no fleas were found on it. Rat D 7 was then put into a 

 freshly-prepared cage by itself. A healthy, clean tame rat (Rat D 8) was then 

 put into Cage D. 



Rat D 7 was examined on 25/12/09 and was found dead on 26/12/09. 

 28/12 09. — Rat D8was removed from Cage D, was carefully freed from fleas, and was 

 put into a separate cage by itself ; one flea recovered from it was returned to 

 Cage D. A healthy, clean tame rat (Rat D 9) was then put into Cage D. 



Rat D 8 was regulai'ly examined from 29/12/09 till 3/1/10, when trypano- 

 somes were first seen in its blood. Permanent snieais were then made from 

 3/1/10 till 8/1/10, when the multiplication-period came to an end. 

 3/1/10. — Rat D9 was removed from Cage D, was carefully searched for fleas, but no 

 flea was found on it and it was put into a separate cage by itself. A healthy, 

 clean tame rat (Rat D 10) was then put into Cage D. 



Rat D9 was regularly examined from 1/1/10 till 4/1/10, when trypanosomes 

 were first seen in its blood. Permanent smears were then made from 4/1/10 

 till 10/1/10, when the multiplication-period came to an end. 

 (Experiment still proceeding — see below.) 



Rcmarhs. — It should be noted that on some occasions considerable numbers 

 of fleas were recovered from the experimental rats in Experiment D, 

 e.g., 54 fleas on December 13, 38 fleas on December 15. As these fleas were 



VOL. LXXXII. — B. z 



