528 FAMILY: TRYPAXOSOMID^ 



of cerebro-spinal fluid to vary from 15 to 467. The blood leucocytes in 

 these cases varied from 4,500 to 12,000 per c.mm. 



Keratitis is common in animals infected with pathogenic trypanosomes, 

 and it occurs less commonly in man. In the case of animals, Morax 

 (1906, 1907) and Yorke (1911) showed that the condition was due to the 

 presence of large numbers of trypanosomes in the lymph spaces, w^hich 

 were often swollen and oedematous. 



Morphology. — T. gambiense, after its inoculation into man by Glossina 

 palpalis, presumably invades the blood and lymphatic channels, and there 

 multiplies by repeated longitudinal division. On account of its scarcity 

 in the blood of man, its morphology has been studied chiefly in the blood of 

 susceptible animals. In the blood of such an animal as the rat or guinea- 

 pig the trypanosome varies in length between 15 and 30 microns, and, as 

 pointed out by Minchin (1908), occurs in three types, for which reason it 

 is regarded as a polymorphic tryjianosome (Plate V., a, p. 456). There is 

 a short and broad form w^hich has no flagellum, a long thin form with a 

 flagellum, and an intermediate form (Fig. 222, A-C). These three types 

 are not sharply defined, as they merge into one another by inappreciable 

 gradations. Robertson (19126) has shown that the short forms are the 

 result of division of the long ones, and that they grow into long forms 

 which divide. The majority of trypanosomes in any infection come 

 within the dimensions given above, but longer forms are sometimes seen 

 nearly 40 microns in length. These are generally dividing forms. On the 

 other hand, trypanosomes less than 15 microns in length are seen, 

 especially in inoculated rats and guinea-pigs. The occurrence of peculiar 

 short stumpy forms in the blood of a guinea-pig inoculated with the 

 South Nigerian human trypanosome combined with its low virulence for 

 human beings, especially in children, led Macfie (1913a) to suggest its 

 separation as a distinct species, T. nigeriense (Fig. 222, D). As these 

 very short forms occur in rats inoculated from human beings with un- 

 doubted T. gambiense, and as the virulence of this trypanosome for man 

 varies considerably in other parts of Africa, it is highly probable that 

 Macfie's trypanosome is merely a strain of T. gambiense of exceptionally 

 low virulence. 



In T. gambiense the nucleus, occupies a central position and the kine- 

 toplast a point a short distance from the posterior end of the body. As 

 regards the undulating membrane, it is of moderate width and not markedly 

 convoluted, being more so than in T. lewisi and less so than in some of the 

 other pathogenic trypanosomes. Granules of volutin may or may not 

 be present in the cytoplasm. Multiplication is by longitudinal division in 

 the usual manner, and calls for no special remark. The supposed sexual 

 process associated with the production of " latent bodies " described by 



