1912 ENTOMOLOGICAL SOCIETY. 47 



men are compelled to agree that entomological knowledge plays a serious part in 

 the welfare of mankind. The ultimate destiny of man, I take it, is the overcoming 

 of the antagonistic forces of nature and of these forces, as we all know, insects 

 constitute an important section. In spreading over the world, the white man 

 has proceeded in a blundering fashion, obsessed by the idea of his own ability to 

 overcome all obstacles, and he has been compelled to pay a heavy price for his 

 pride. Finally, he is forced to tread the thorny path of knowledge, and to 

 learn only by diligent inquiry the means whereby he can rectify the errors of the 

 past and prevent their recurrence in the future. Time will not permit more 

 than a brief account of two diseases which have had a most profound influence 

 on mankind. These are the Sleeping Sickness and Malaria. 



Before describing the nature and cause of the Sleeping Sickness, it is neces- 

 sary to discuss another disease, the discovery of the cause of which led up to 

 the discovery of the causative organism of the Sleeping Sickness. 



African travellers for years have been well acquainted with a certain fly known 

 as Tse-tse Fly, which occurs in certain parts of Africa in districts known as "Fly 

 Belts." The presence of this fly rendered impossible the use of horses as beasts 

 of burden, and its bite was also known to be fatal to cattle and dogs. It was 

 not until 1895 that Col. Bruce, by means of series of patient investigations, 

 discovered that the deadly nature of this fly was due to the fact that it was the 

 carrier of a microscopic parasitic organism to which the name of "Trypanosoma" 

 was given. He showed that " Nagana," as this disease of cattle is called, was due 

 to the inoculation of the animal by the fly with a species of Trypanosome. 



Although domestic animals are highly susceptible to the disease, he found 

 that the native big game such as buffaloes, antelopes, etc., normally carried these 

 parasitic organisms in their blood without experiencing any ill effects as they, by 

 long selection, had become immune and they served as reservoirs from which flies 

 obtained the organisms. In 1901, the dread disease of Sleeping Sickness was 

 first noticed in Uganda, and the severity of the disease is indicated by the fact 

 that in a single island, Buvuma, the population was reduced from twenty-two 

 thousand to eight thousand in a very short time, and in Busoga the deaths in 

 one year from the disease numbered twenty thousand. A disease of this character 

 was bound to attract the attention of the responsible governments, and investi- 

 gations were immediately initiated. Col. Bruce was sent to Uganda, and he 

 found in the cerebro-spinal fluid of natives suffering from the disease a species 

 of Trypanosome. His previous work on Kagana led him to the belief of a 

 possible relationship of a biting fly to the disease, and he immediately had 

 collections of biting flies made throughout the entire region north of Lake 

 Victoria Nyanza. He also mapped out the localities in which the disease occurred. 

 As a result he found that the incidence of the disease corresponded with the 

 distribution of a certain species of Tse-tse Fly {Olossina palpalis). The species 

 which was the carrier of the causative organism of the cattle disease, Nagana, 

 was Glossina morsitans, and these Tse-tse Flies of the genus Olossina are nearly 

 related to our own Stable Fly, Stomoxys calcitrans. Col. Bruce was able to show 

 by a series of experiments that the Tse-tse Fly was able to transmit the disease 

 to healthy monkeys. The Trypanosome was found in the blood of natives, but 

 did not appear to do much harm until it reached the cerebro-spinal canal, where 

 it gave rise to the disease. Sleeping Sickness. The initial stages of the disease 

 were accompanied by a strong disinclination to work on the part of the natives. 

 The lymphatic glands became swollen, and in the end the patient sank into a state 



