76 THE ANIMAL PARASITES OF MAN 



crithidial type. The second development in the salivary gland is the 

 essential feature. The short, stumpy forms of trypanosomes (fig. 30, e) 

 finally produced in the salivary glands are alone infective. No 

 conjugation of trypanosomes occurs in the fly. Only about 5 per 

 cent, of captive tsetse flies fed on trypanosome-infected blood become 

 infective, but they probably remain infective for the rest of their lives. 



J. G. Thomson and Sinton (19 12) 1 have obtained in cultures the 

 various trypanosome forms of T. gambiense seen in the fly's main gut. 



Duke (19 1 2) 2 found T. gambiense in a species of antelope, the 

 situtunga (Tragelaphns spekei), on Damba Island in Victoria Nyanza. 

 Wild G. palpalis could be infected therefrom. The antelope may 

 then act as a sleeping sickness reservoir in that district, but men are 

 apparently the chief reservoir. 



Trypanosoma nigeriense, Macfie, I9I3. 3 



Macfie has recently (August, 1913) described a human trypano- 

 some from the Eket district of Southern Nigeria. It is common in 

 young people. The disease produced does not seem to be of a 

 virulent type in Nigeria, and does not occur in epidemic form. In 

 the early stages the glands of the neck are enlarged. In the later 

 stages cases of which are rarer lethargy appears. The parasite 

 is a polymorphic trypanosome, morphologically almost indistinguish- 

 able from T. gambiense, though it may be slightly shorter. Macfie 

 recorded the occurrence in his preparations of a few trypano- 

 somes appearing to have a flagellum free during their whole length. 

 Some of the parasites, as seen in a sub-inoculated guinea-pig, are very 

 small (8 IJL long). Other trypanosomes have their nuclei displaced 

 somewhat anteriorly. This parasite may only be a variety of 

 T. gambiense. The parasite is perhaps spread by Glossina tachinoides. 



Trypanosoma rhodesiense, Stephens and Fantham, 1910. 



The parasite was found in the blood of a young Englishman who 

 had contracted sleeping sickness in the Luangwa Valley, North- 

 eastern Rhodesia, in the autumn of 1909. The patient had never 

 been in an area infested with Glossina palpalis. 



(i) Morphology. The morphology of the parasite in man and 

 sub-inoculated rats was studied by Stephens and Fantham in 1910. 4 

 They pointed out a morphological peculiarity in the presence of 

 certain trypanosomes with posterior nuclei in sub-inoculated animals, 

 that is, parasites in which the nucleus (trophonucleus) was situated 

 towards the posterior or aflagellar end, close up to or even beyond the 



1 Annals Trap. Med. and Parasitol. , vi, p. 331. - Proc. Roy. Sac., B, Ixxxv, pp. 156, 483. 

 3 Annals Trop. Med. and Parasitol. , vii, p. 339; viii, p. 379. 

 * Proc. Roy. Sec., B, Ixxxiii, p. 28. 



