26 
NOTES ON THE COMMON PATHOGENIC 
T. gambiense. Dutton, 1902. The parasite of sleeping 
sickness or trypanosome fever in man. 
Distribution. In East Africa it is confined to the vicinity 
of Lake Victoria and a few of the larger tributary rivers. 
Hosts. Man ; probably cattle and game (Bruce, Ham- 
merton, Bateman, and Mackie) ; Glossina palpalis. 
Morphology. Average length about 18/<t to 25ya, breadth 
1*4 >l 6 to 2 p with a free flagellum of 5p to Ip. 
Biology. Capable of development in most domestic animals 
and the smaller laboratory species as rats, guinea-pigs, and 
rabbits. Duration of disease in these species usually long, and 
trypanosomes scanty in the blood. Culture in vitro has only 
been partly successful. 
Transmission. The coincidence of T. gambiense and 
Glossina palpalis led to the view that this fly is a specific host, 
and Bruce and Nabarro showed that infection could be trans- 
mitted by its agency. The work of Kleine, and subsequently 
that of Bruce, Hammerton, Bateman, and Mackie, has shown 
that a developmental cycle must take place in the fly, since 
a period of at least sixteen days elapses between the time the 
trypanosomes are ingested with the blood and the period when 
the fly becomes infective. This infectivity once established 
may last at least fifty days. Owing to the frequent presence 
of flagellates peculiar to the tsetse flies, as, for example, Try- 
panosoma or Herpetomonas grayi, the developmental forms 
of which in the gut cause much confusion, details of the cycle 
of T. gambiense have not been clearly made out. 
Prior to the discovery of this true cyclical development all 
successful transmission experiments had been of a mechanical 
nature, i.e. the trypanosome was presumably conveyed from 
the sick to the healthy animal on the proboscis. Such trans- 
mission might in theory be effected by any biting fly, and 
Nabarro and Greig proved that flies (Gl. fusca, Gl. longipennis , 
Gl. pallidipes) caught at Kibwezi in this Protectorate could 
transmit infection eight hours and twenty-four hours after the 
infecting meal. 
Decently a number of cases of human Trypanosomiasis have 
been found in the Loangwa Valley, Northern Rhodesia, where 
no Gl. palpalis have yet been discovered despite careful and 
