ATURAL1ST [Vol. XLIII 



from a theoretical standpoint, have maintained that the fly stood 

 in the same relation to the disease as the mosquito held to 

 malaria. As already indicated, the definite evidence thus far 

 secured has seemed to favor the view that the fly is a mere me- 

 chanical agent. Some recent experiments in East Africa are of 

 tremendous importance in this discussion. Kleine 1 under date of 

 December 28, 1908, reports from Kirugu, German East Africa, 

 an experiment which apparently demonstrates that flies may 

 infect after a long interval. Heretofore it has been claimed 

 that flies would not infect later than forty-eight hours after 

 biting infected hosts. A longer interval is good evidence of 

 the existence of a developmental cycle in the fly. K N ine's 

 experiment may he summarized as follows: 



Xanana, an animal disease due to T i\u pa nosoma Bntcii. docs 



naturally infected by the bite of the tse-tse fly. (Ilnsslna 

 morsifans. were brought from a locality seven days' march dis- 

 tant and were kept in isolation. Other flies, Glossina palpalis, 

 caught on the Mori River, were fed for three days on the in- 

 fected animals and from the fourth to the seventeenth day 

 inclusive for each day on a fresh healthy animal. From the 

 eighteenth to the twenty-fourth day the' flies fed on a single 

 sheep ; from the twenty-fifth to the twenty-ninth day on a single 

 ox. Frequent blood examinations were made of the experi- 

 mental animals and on the twelfth day after the flies were put 

 on the ox which was first used on the twenty-fifth day of the 

 experiment, numerous trypanosomes were found in the blood of 

 this host. Then the sheep first employed as host on the eight- 

 eenth day was examined and found also to be infected. All 

 the other experimental animals remained uninfected. Goats, 

 calves and sheep were used to feed the flies from the fortieth 



"From this it is seen that flies which for many days after the 

 ingestion of blood containing trypanosomes we're not infective, 

 afterwards became so and infected a sheep and then an ox." 



The Royal Society has received a telegram dated April 3 from 

 Colonel Sir David Bruce which announces the confirmation of 

 Kleine 's observations, and a letter received April 30, dated 

 Mpumu, Chagwe, Uganda, April 3, confirms the cablegram 



palpalis." Deutsche medizinische Work, „.srl,ri ft . Is Mar/.. !'.»<»*.» : 4f>! , -»""- 



