370 
Mammalian Trypanosomes of Africa 
The acute nature of the disease in dogs characterises all the strains, 
being most marked with the antelope strain both as regards the rapidity 
of the disease and the early onset of the corneal symptoms. 
The behaviour of the human strain is, however, very different. In monkeys 
the incubation period is prolonged and trypanosomes are always rare in the 
blood. Four attempts to infect guinea-pigs, and two inoculations of rabbits 
failed to produce infection. 
Baboons, incidentally, appear to be immune to both strains; laboratory- 
bred flies, proved to be infective before and after, carrying the human and 
wild-fly strains, were fed on baboons without any sign of infection resulting 
in either case. Both animals were examined by daily blood examination of 
stained thick and of fresh films, and, in the case of the human strain, by 
sub-inoculation. 
When first isolated in the original monkey (M 173) this 1920 antelope strain 
appeared to be characterised by peculiar movements, distinct from those of 
the mainland wild-fly strain. The long forms showed a definite translatory 
movement, progressing in a steady snake-like manner across the field. Sub¬ 
sequent investigation has, however, shown that while this movement is more 
often seen with the antelope strain, it is also exhibited by the wild-fly strains 
in various animals. 
(d) Posterior-nuclear forms. 
The appearance of definite posterior-nuclear forms in guinea-pigs inocu¬ 
lated with these strains is of considerable interest. Such forms have not been 
hitherto described from the Uganda lake-shore fly area, though Blacklock 
found them in a European strain of the Uganda T. brucei, which, however, 
did not emanate from the lake-shore fly zone (Blacklock, 1912). 
These forms were most numerous in guinea-pigs infected with the Damba 
antelope strain. Thus in P 198, on the day before its death, posterior-nuclear 
forms amounted to 15-2 per cent, of the short individuals counted, these short 
forms predominating in the blood, while trypanosomes with the nucleus 
anteriorly displaced amounted to 4*2 per cent. In P 240, Damba flv strain, 
posterior-nuclear forms were rarer, but a day or two before death amounted 
to 3 per cent, of all trypanosomes present, while a few anterior-nuclear forms 
were also seen. 
X2000. Camera lucida, e and / from guinea-pig 241, others from guinea-pig 198. 
