540 FAMILY: TRYPANOSOMIDiE 



This trypanosome was discovered by Bruce in 1895, and proved to be 

 one of the causes of nagana, a disease which had long been known to 

 attack domestic animals in Zululand. Accounts of his observations were 

 published in 1897 and 1903. The trypanosome was named Trypanosoma 

 brucii {T. brucei) by Plimmer and Bradford (1899), from the forms which 

 occurred in an infected dog which had been sent to England by Bruce. 



Stephens and Blacklock (1913) noted that the strain was monomorphic, 

 and resembled T. evansi rather than the polymorphic form here described 

 as T. brucei. Plimmer and Bradford (1899) described their trypanosomes 

 as monomorphic, hence Stephens and Blacklock think that the poly- 

 morphic Uganda trypanosome, which is now generally called T. brucei, 

 cannot be the same as the original monomorphic Zululand trypanosome, 

 the true T. brucei. They therefore suggest the name T. ugandce for the 

 polymorphic form. Bruce, on the other hand, regards his original Zululand 

 strain as the same as the polymorphic form now generally known as 

 T. brucei, and ascribes the discrepancy to a change in type which has 

 probably taken place owing to long maintenance in laboratory animals. 

 That some profound change had taken place receives support from 

 Roubaud's observations (1913) that the Pasteur Institute strain was no 

 longer capable of infecting Glossina morsitans. The writer has noted on 

 several occasions that trypanosomes inoculated from the blood of man into 

 laboratory animals may show posterior nuclear forms at first, and that these 

 disappear entirely in subsequent passages, the trypanosomes tending to 

 become more and more monomorphic. The figure given by Bruce (1897) 

 of the trypanosome in the blood of the dog shows definitely a polymorphic 

 form, while one of the trypanosomes appears to have the nucleus in a 

 posterior position. 



There can be no doubt that one of the trypanosomes causing nagana is 

 really a polymorphic trypanosome, whatever Plimmer and Bradford said 

 about the strain they examined in 1899. It is quite possible that they over- 

 looked or neglected to describe the forms without flagella, a point which 

 can only be determined by a re-examination of their original films. It is 

 worthy of note that, though T. brucei had been studied by many observers, 

 posterior nuclear forms had not been described till Stephens and Fantham 

 (1910) noted them in T. rhodesiense, the cause of a disease in man. This 

 trypanosome is indistinguishable from T. brucei, and will be regarded as 

 the human strain of this species. The question is more fully discussed 

 below. 



Distribution. — The polymorphic trypanosome which was named by 

 Plimmer and Bradford (1899) is now known to be of wide distribution in 

 Africa, extending from the Sudan to Zululand, though it has frequently 

 been described under different names. It has been recorded from the 



