24 



Sir D. Bruce and others. Trypanosome 



Comparison of the Theee Strains in regard to their Virulence 

 towards Various Animals. 



Table XVII. — The Average Duration of the Disease in Various Animals, in 



days. The letter E means that the animal is refractory, that is, not 

 susceptible to the disease. 



Strain. 



Donkey. 



Ox. 



Goat. 



Pig- 



Monkey. 



Dog. 



Guinea-pig. 



White rat 



Mvera Cattle 



87? 



103? 



64 







34 



E 



E 



Wild Game 







56 





142 



74 



E 



30 



Wild. (?. morsitans 





140 



46 



21 



117 



37 



41 



37 



On the whole it may be concluded that the Wild G. morsitans strain is the 

 most virulent. 



Table XVIII. — The Percentages of Eecoveries in Various Animals from the 

 Three Strains. The letter E stands for refractory. 



Strain. 



Donkey. 



Ox. 



Goat, 



Pig. 



Monkey. 



Dog. 



Guinea-pig. 



White rat. 



Mvera Cattle 



80 



37 • 



14 











E 



E 



Wild Game 







17 













E 







Wild G. morsitans 









6 









2 











It must be confessed that the margin of error in a table such as this must 

 be enormous ; the fallacies are many. It is difficult or impossible to say 

 when or if an animal has recovered from a trypanosome disease. The 

 numbers employed are often small. For example, there is per cent, 

 indicated in regard to Guinea-pig, Wild game strain. This animal is returned 

 as refractory, but there was only one experiment. It is evident that it would 

 be more satisfactory if, say, a minimum of 10 animals of each species was 

 used in studying each different strain. But in the wilds of Nyasaland this is 

 a counsel of perfection impossible to attain. At the present time the 

 Commission finds the greatest difficulty in obtaining small numbers of such 

 local animals as goats, monkeys, and dogs, while as to the smaller laboratory 

 animals, they must come from England. This entails a heavy mortality, as 

 may be judged from the fact that of the last consignment of 25 guinea-pigs 

 and 50 rats only 9 of the former and 12 of the latter arrived at Kasu alive. 



The Average Duration of Life, in days, of Various Animals infected 

 by T. pecorum, Nyasaland. 

 The following table combines the results obtained from a study of the 

 susceptibility of various animals to each of the three strains, so as to arrive at 



