1913.] 



Glossina morsitans in Nyasaland. 



425 



Table II. — The Number of Times a Monkey, Dog, and Goat became infected 

 with Trypanosoma brucei vel rhodesiense, T. pecorum, T. simia;, and T. caprce, 



in a Series of 56 Experiments, averaging 180 Tsetse Flies each. 



T. brucei vel 

 rhodesiense. 



T. pecorum. 



T. simia. 



T. caprce. 



Monkey. 



Dog. 



Goat. 



Monkey. 



Dog. 



Goat. 



Monkey. 



Dog. 



Goat. 



Monkey. 



Dog. 



Goat. 



9 



14 



11 



9 



34 



35 



26 







17 











35 



This shows that the monkey is less susceptible to T. brucei and T. pecorum 

 than the dog, whereas it is remarkably so to T. simicc. The dog is not 

 susceptible to T. simice, and neither the monkey nor dog to T. caprce. 



Table III.— The Proportion per 1000 Tsetse Flies, caught in the " Sleeping- 

 Sickness" Area of Nyasaland, found to be Infective with Pathogenic 

 Trypanosomes. 



T. brucei vel 

 rhodesiense. 



T. pecorum. 



T. simia. 



T. caprce. 



Per 1O0O. 

 2 -0 



Per 1000. 

 4-6 



Per 1000. 



3-4 



Per 1000. 

 3 -5 



This is only allowing one infective fly to each series of flies fed on the 

 experimental animals, and is therefore the irreducible minimum. The 

 average number of flies fed on each animal was 180, and it might well be 

 that there were present in the same batch several flies infective with the 

 same species of trypanosome. Ten thousand flies gave rise to 135 infections, 

 and taking it for granted that no fly was infective with more than one 

 species of trypanosome, then 13 - 5 per 1000 flies are infective with one or 

 other of the disease-producing trypanosomes of this district. 



Table IV. — Number of Times the Species of Trypanosomes under 

 consideration were found in 56 Experiments. 



T. brucei vel 

 rhodesiense. 



T. pecorum. 



T. simia. 



T. capra. 



20 



46 



34 



35 



35'7 per cent. 



82 "1 per cent. 



60 - 7 per cent. 



62 o per cent. 



VOL. LXXXVI. — B. 2 I 



