INSECTS AND MANKIND 429 



the causal organisms of various human diseases. The 

 demonstration and recognition of this dangerous connection 

 between insects and mankind have proved a noteworthy 

 scientific achievement of recent years, and '' medical 

 entomology " has become a fascinating subject of investiga- 

 tion at which the physician, the bacteriologist or protozoo- 

 logist, and the student of insects may work in fruitful 

 comradeship. 



Just as the African Tsetse-fly Glossina morsitans transmits 



to cattle and horses the protozoan Trypanosoma hrucei that 



causes '* nagana " disease (pp. 411-412), so another species 



of Tsetse, G. palpalis, is the carrier and transmitter of 



Trypanosoma gamhiense^ which in man, migrating from the 



blood into the central canal of the nervous system, gives 



rise to the fatal disease which from its characteristic 



symptoms is known as " sleeping-sickness." The stor}^ of 



the discovery by which these facts have been established 



during the present century is well told by Hale Carpenter 



(1920). The Trypanosoma was first detected in Gambia 



in 1901 by Forde, who found it in the blood of an English 



patient displaying febrile symptoms, and the nature of the 



blood parasite was determined the next year when Dutton 



had opportunity of examining the patient in Liverpool. 



Then, in 1903, Castellani demonstrated the presence of 



Trypanosoma gamhiense in the cerebro-spinal fluid of native 



Africans afflicted with sleeping-sickness, a disease long 



prevalent in the western part of the continent, always fatal, 



and though attacking large numbers of people, not appearing 



as an epidemic to the destruction of a high proportion of 



the inhabitants. It was in Uganda, in East Central Africa, 



that the disease appeared as an alarming threat to the health 



and survival of a great community. Dr. A. Cook, of the 



Mission Hospital at Mengo, recognised the disease in 1901 



as a new and mysterious outbreak, for by the end of that 



year two hundred Baganda had died and thousands were 



aflfected, while in 1906 the Governor of the Protectorate 



reported that during the preceding five years '' the total 



mortality from this scourge had considerably exceeded 



