576 ANNUAL, REPORT SMITHSONIAN INSTITUTION, 1921. 



us to whether the fly was simply a mechanical carrier of the patho- 

 genic organism or whether it was a necessary secondary host. This 

 point was partly cleared by Koch, who discovered what he consid- 

 ered to be sexual forms of the trypanosome in the intestine of the 

 fly, but Kleine in 1909 succeeded in finding the different stages of 

 the parasite in the intestine of the insect and proved that part of the 

 life cycle of the insect must occur in this secondary host. 



Bruce's discovery and the work of others who followed him in 

 the study of the Nagana disease led directly to the discovery of the 

 cause of the terrible sleeping sickness of man in Africa by Dutton 

 in 1902, which was confirmed by Castellani a little later. When this 

 discovery was announced the Frenchman, Brumpt, and Sambon in 

 England advanced at once the theory that this disease is also trans- 

 mitted by a tse-tse fly. Their argument was based upon Bruce's dis- 

 covery with the Nagana and also upon the geographic distribution 

 and epidemiology of the disease, and their theory was abundantly 

 demonstrated not long after by practical experimentation. In this 

 case Sambon was much more fortunate than he was some years later 

 when he advanced the theory that Pellagra is carried by the black 

 flies of the genus Simulium, which was afterwards abundantly dis- 

 proved. 



The serious and fatal disease called " Sleeping sickness " had 

 been known among the natives of parts of Africa for very many 

 years. The earliest published account that has been found was by 

 a naval surgeon, John Atkins, in a book entitled " Physical Observa- 

 tions on the Coast of Guiney," published in 1741. For a long time 

 the disease seemed to be limited to West Africa, but with the opening 

 up of the interior it found its way into Uganda with terrible re- 

 sults. In 1901 it was reported by Dr. Albert Cook, of a missionary 

 society, that 200 natives had died and thousands appeared to be in- 

 fected on Buvuma Island. The disease spread with dreadful rapid- 

 ity and the Government became intensely alarmed. A commission 

 was sent out from England under the auspices of the Royal Society, 

 and such men as Low, Christie, Castellani, and Sir David Bruce be- 

 gan an immediate investigation, which has continued without inter- 

 ruption (except for the period of the Great War) until the present 

 time. An international sleeping sickness congress was held in Lon- 

 don in 1907, which was attended by the most eminent pathologists and 

 parasitologists of many nations, including especially those having 

 African colonies. During all the early stages of the investigation 

 and for a number of years after it was discovered that the disease 

 was carried by the tse-tse flies, field investigations were carried on 

 exclusively by medical men. E. E. Austen, of the British Museum, a 

 well-known entomologist, especially skilled in the diptera (the order 

 to which tse-tse flies belong) was consulted as to the taxonomy of the 



