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



20/12/09. — Rat CIO was removed from Cage C, was cai'efully freed from fleas, and was 

 then put into a separate cage by itself. 6 fleas recovered from it were put back 

 into Cage C. A healthy, clean rat (Rat C 11) was then put into Cage C. 



Rat C 10 was examined regulai'ly from 21/12/09 till 26/12/09, when trypano- 

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

 26/12/09 till 30/12/09, when the multiplication-period came to an end. 

 22/12/09. — Rat Cll was removed from Cage C, was carefully examined for fleas by aid 

 of chloroform-vapour, but no flea was found on it. It was put into a sepai-ate 

 cage by itself. A healthy, clean tame rat (Rat C 12) was then put into Cage C. 

 Rat Cll was examined regularly from 23/12/09 till 28/12/09, when trypano- 

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

 28/12/09 till 1/1/10, when the multiplication-period came to an end. 

 24/32/09. — Rat C12 was removed from Cage C, was carefully freed from fleas, and was 

 put into a separate cage by itself ; 9 fleas recovered from it were returned to 

 Cage C. A healthy, clean tame rat (Rat C 13) was then ])ut into Cage C. 



Rat C12 was examined on 25/12/09 and was found dead on 26/12/09 before 

 trypanosomes had time to appear in its blood. 

 28/12/09. — Rat C 13 was removed from Cage C, was carefully freed from fleas, and was 

 put into a separate cage by itself ; 3 fleas recovered from it were returned to 

 Cage C. A healthy, clean tame rat (Rat C 14) was then put into Cage C. 



Rat C13 was examined regularly from 29/12/09 till 3/1/10, when trypano- 

 somes were first seen in its blood. Permanent smears were made from 3/1/10 

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

 31/12/09.— Rat C 14 was removed from Cage C, was cai-efully searched, but no flea found 

 on it, and was put into a separate cage by itself. A healthy, clean tame rat 

 (Rat C 15) was then put into Cage C. 



Rat C 14 was examined regularly from 1/1/10 till 22/1/10. No trypanosomes 

 were found in its blood at any time. 



(Experiment still proceeding — see below.) 



Experiment D. 



6/12/09. — 254 fleas from the breeding cage were put into the freshly-prepaied and 



cleaned special tin cage. 

 7/12/09. — A heavily-infected tame rat showing many trypanosomes in its blood, after 

 being carefully searched with chloroform-vapour to ensure that it harboured no 

 fleas, was put into the above-mentioned tin cage at 2 p.m. 

 8/12/09. — 212 fleas were recovered from the above cage and rat (203 from the cage and 

 9 from the rat) at 12 noon. Of these, 162, including the 9 from the rat, were 

 put into the freshly-prepared flea-])r()of cage (Cage D), together with a healthy, 

 clean tame rat (Rat 1)1), and the remaining 50 (all from the cage) were ])ut 

 into another cage (Cage E), with another healthy, clean tame rat (Rat E 1). 

 11/12/09. — Rat Dl was removed from Cage D, was carefully freed from fleas by the aid 

 of chloroform- vapour, and was put into a separate freshly-prepared flea-proof 

 cage by itself. 20 fleas recovered from Rat 1) 1 were returned to C^age D. A 

 clean, healthy tame rat (I) 2) was ))ut into (hge I). 



Rat 1> 1 was examined regularly from 14/12/09 until 22/1/10. No tryj)ano- 

 Homes were found in its blood at any time. 

 13/12/09. — Rat D 2 was removed from Cage ]J, was carefully freed from lloas, and was 

 then put into a separate freshly-prepared flea-proof cage by itself. 54 fleas 

 recovered from Rat J) 2 were returned to ( !age D. 



