186 



Colonel Sir D. Bruce. 



[May 19 



Comparison of Trypanosoma evansi and Trypanosoma brucei. 

 Up to the present it has been usual to look upon Trypanosoma evansi and 

 Trypanosoma Irucei as being indistinguishable morphologically. It will 

 therefore be interesting to compare the curves of these two species of 

 trypanosomes. 



Chart 4. — Chart giving Curves representing the Distribution, by percentages, in respect 

 to Length of Trypanosoma evansi and Trypanosoma brucei. 



Microns 



13 14- 15 16 17 18 19 2Q 21 22 23 24 25 26 27 28 29 3Q 5 I 32 35 34 35 













































































































































































































V 







































































































































y 















































































T. evens/ 



T. brucei 



These curves are very unlike. It is therefore evident that if this method 

 of recognising species of trypanosomes proves to be true, there ought in 

 future to be no difficulty in separating these two species by this means alone. 

 It might not always be possible to separate them by examining a single 

 specimen of blood from each. Let us say a species of trypanosome is found 

 in the Sudan, and it is a question of deciding whether it is Trypanosoma h*ucei 

 or Trypanosoma evansi. It is inoculated into several animals — the horse, ox, 

 monkey, dog, rabbit, guinea-pig, and rat. Two specimens of blood are made 

 from each species on different days — 40 trypanosomes from each species, 

 280 in all. If time were available, it would be better to measure a thousand. 

 Then, if it is found that the curve lies mostly between 18 and 30 and not 

 between 13 and 35, the diagnosis would be Trypanosoma evansi. 



The average length of 172 Trypanosoma Irucei was found to be 

 23'6 microns ; thit of Trypanosoma evansi, 24 - 9. It would, therefore, not be 

 possible to separate these two species by length alone. Even if they are 

 measured more minutely the result is the same. 



For Table III, 180 Trypanosoma evansi and 91 Trypanosoma Irucei have been 

 measured and the average taken. 



