4i8 



TRYPANOSOMIDm 



1. Trypanosoma gambiense 'Dniton, 1902. 



2. Trypanosoma castellanii Kmse, 1903. 



3. Trypanosoma vivax Ziemann, 1905, varietas macfiense. 



4. Trypanosoma cruzi Chagas, 1909. 



5. Trypanosoma rhodesiense Stephens and Fantham, 1910, 



6. Trypanosoma nigeriense Macfie, 1913. 



7. Trypanosoma gambiense varietas longum Da Costa, St. Anna, 

 Dos Santos, and Alvares, 1915. 



When a classification is desired it is always necessary to attempt 

 to discover the characters of the original species, which in this case 

 is T. gambiense Dutton, 1902. Sixteen years have passed since the 

 slides containing the original specimens of Dutton and Todd were 

 made, and, therefore, as the original strain has long been lost, the 

 only method of comparing other organisms with the original speci- 

 mens is morphological. Chalmers and O'Farrell have made this 

 comparison by measuring one thousand non-dividing forms in the 

 original slides. As far as measurements go, these strains are very 

 similar, but, as we have repeatedly insisted, morphology often may 

 not help in separating closely related but perhaps quite distinct 

 species, which require to be studied serologically and with regard to 

 animal pathogenicity, and, in cases of human infection, with regard 

 to the nature of the disease in man. Thus Stephens has pointed 

 out that T. lewisi and T. rabinowitschi, T. brucei and T. evansi, T. 

 pecaudi and T. ugandce, T. rhodesiense and T. pecaudi are indis- 

 tinguishable morphologically, but are distinct biologically. 



We mention these points in order to make clear to the reader the 

 necessity of comparing human trypanosomes by means of the clinical 

 features of the disease in man, the serum reactions and animal 

 experiments, as well as by morphological characters, and we 

 have suggested for years that the name T. gambiense covered a 

 number of different forms, which at the present time is generally 

 admitted with regard to T. rhodesiense. And why not ? Are there 

 not a number of different trypanosomes in wild animals in Africa, 

 and is it impossible that man should from time to time become 

 infected by one of these, even if it does not appear in epidemic form 

 in the human race ? To exemplify we draw attention to an organism 

 resembling T. vivax found by Macfie in man. 



Sir David Bruce believes that T. rhodesiense Stephens and Fantham, 

 1910, is the same as T. brucei Plimmer and Bradford, 1899, but this 

 can hardly be so, because Laveran and Nattan-Larrier have im- 

 munized a ram against T. brucei, and then infected it with T. rhode- 

 siense, an acutely lethal infection ensuing. The serological experi- 

 ments of Chalmers and O'Farrell in vitro and in vivo also show 

 the same marked differences between T. rhodesiense and another 

 posterier nucleate trypanosome. These experiments, to our mind, 

 are more iraportant than measurements, and more important than 

 finding that the development in Glossina morsitans is very similar 

 in both variants. T. rhodesiense may have been derived in recent 



