144 TROPICAL MEDICINE AND HYGIENE 



as the primary sore. In the Congo, and where infection 

 is through G. palpalis, this scar is usually on the legs. In 

 Rhodesia, where the higher flying G. morsitans is the 

 carrier, on the neck. It may not be present. 



The mode of propagation of one of the trypanosome 

 diseases in the horse is by sexual intercourse. With 

 human trypanosomiasis there is no evidence that the 

 disease is spread in this manner. Direct inoculation of 

 the blood of an infected animal into another will transmit 

 the disease, and even an abraded surface is sufficient, but, 

 as far as is known, in nature it is transmitted by the 

 bites of certain flies belonging to the genus Glossina. 



From the distribution of the disease, and the corre- 

 sponding distribution of the flies, G. palpalis is believed 

 to be the important carrier, whilst G. fusca and possibly 

 G. tachinoides may also be carriers. The commonest of 

 the tsetse-flies, G. morsitans, though it carries the trypano- 

 some of nagana, is probably not a carrier of T. gambiense 

 in Uganda or on the Congo, but is the carrier in Rhodesia 

 and on the Zambesi of T. rhodesiensc. 



The Glossinae are a genus limited to Africa and the 

 shores of the Arabian Gulf, and are easily distinguished 

 from other biting flies. 



They are dipterous insects, and closely resemble many 

 of the Muscidae, but are distinguished by the long, straight 

 proboscis, by the arista or spine which arises from the 

 third joint of the antennae being plumose on the one 

 side only, by the palps being the same length as the 

 proboscis and grooved on the inner side, so that together 

 the two palpi form a sheath for the proboscis. There 

 are hairs only on the convex side of the arista and these 

 are compound. The wings are crossed, so that when at 

 rest their tips overlap each other "scissor" wings 

 and project beyond the abdomen. The fourth longitu- 

 dinal vein is bent twice, once to meet the transverse 

 vein, and a second time to approximate to the third 

 longitudinal. 



Glossinae are nearly pupiparous ; the larvae attain their 



