112 



Sir D. Bruce and others. Trypanosome 



If this Naturally Infected Dog strain had been found in the blood of the 

 wild game and in the wild G. morsitans, then it would have been legitimate 

 to make a new species of it. But it would be unjustifiable to make a new 

 species of a strain which, up to the present, has only been found in three 

 chronically infected dogs. The Commission have therefore decided to 

 consider this strain as belonging to the species described as the Trypanosome 

 causing Disease in Man in Nyasaland — Trypanosoma brucei vel rhodesiense — 

 and not as a new species. If this is correct, then it is curious how much 

 a species can vary in disease-producing power. For example, it will be 

 shown that this Naturally Infected Dog strain is almost harmless to 

 monkeys and guinea-pigs, whereas the parent species kills these animals 

 without fail. Not only does it differ in virulence, but even its morphology 

 is apparently somewhat changed. There is a comparative absence of the 

 blunt-ended posterior-nucleated forms, which are sometimes so marked 

 a feature in the parent species. Not that they are altogether absent, but 

 they are not so prominent, do not strike the eye so readily. It will 

 therefore be interesting to describe this strain as fully and completely as 

 possible. 



♦ 



