1913.] causing Disease in Man in Nyasaland. 



301 



Chart 14. — Curve representing the Distribution, by Percentages, in respect to Length, of 

 3600 Individuals of the Human Strain of the Trypanosome causing Disease in Man 

 in Nyasaland, taken from the rat alone. 





M i c r o n s 



1 3 



14 



15 



16 



1 7 



1 8 



I g 



20 





22 



23 



TLA 



25 



26 



9*1 



*= / 



28 



29 





3i 



32 



33 



3 A- 



35 



36 



37 



38 



II 























































9 



CO 



J> 8 

 .ol) 

 d 7 



Z 5 

 % + 



°- 3 

 z 

 1 















































































































































































































































































































































































































































































































































■ At 

















































Curves 13 and 14 will be found of use when the human strain of this 

 species of trypanosome is compared with the Wild Game and the Wild 

 Glossina morsitans strains. 



Table XX. — Comparison of the Percentages of Posterior-Nuclear Forms found 

 among the Short and Stumpy Varieties of the Trypanosome of the Human 

 Strain. 



Experiment 

 No. 



Strain. 



Name. 



Animal. 



Percentage among short and 

 stumpy forms. 





I 



Mkanyanga 





Rat 



34-1 



728 



II 



E 







9-3 



953 



III 



Chituluka 





» 



10 -3 



1337 



IV 



Chipochola 







3 3 



16C0 



V 



Chibibi 







32 -0 





17 -8 



It is to be noted that in the human strain the percentage of posterior- 

 nuclear forms varies greatly, although the method of enumeration is the 

 same in each case. This presence of posterior-nuclear forms would have 

 been accepted a few months ago as sufficient proof that the species dealt 

 with was T. rhodesiense. Since then posterior-nuclear forms have been 

 reported as occurring in T. brucei from Egypt, Uganda and Zululand. In a 

 strain lately obtained by Theiler from the same spot in Zululand where 

 this species was originally discovered in 1894, this percentage rose to 

 the highest yet recorded. 



VOL. lxxxvi. — B. z 



