C. DOBELL 207 



Kudicke (1911) made a further attempt to discover how Werbitzki's 

 straia had lost its kiuetonuclei. He says that even in normal races of 

 Trypanosomes — that is, in organisms untreated with dyes — as many as 

 5 7o of the individuals may lack kinetonuclei. It is therefore possible 

 that the drug selects these organisms : they may be more resistant to 

 the drug, and therefore survive after treatment and so give fise to the 

 new race. Kudicke was unable, however, to discover exactly how 

 the kinetonucleus disappeared. He found that acridin would remove 

 the kinetonucleus from T. levrisi — in a certain percentage of cases — 

 but here again he was unable to decide with certainty how the removal 

 was brought about. Kudicke's work, on the whole, did not show 

 whether the races of Trypanosomes without kinetonuclei were pro- 

 duced by selection, by an irregular division, or in some other way. 



An important sequel to Werbitzki's work has been furnished by 

 Laveran and Roudsky. Laveran (1911) obtained the"nagana ferox" 

 and " Werbitzki " strains of T. brucei from Ehrlich. He was able to 

 confirm Werbitzki's observations on the structure of the individuals 

 composing these strains. In collaboration with Roudsky (1911), he 

 reinvestigated the action of oxazin upon T. brucei. These workers 

 found that the dye removed the kinetonucleus — as Werbitzki had 

 stated. They were able to extend the investigations, moreover, to 

 seven other species of Trypanosomes (evansi, soudanense, gambiense, 

 diniorphon, pecorum, congolense, lewisi). In all of these, oxazin caused 

 a disappearance of the kinetonucleus : and the peculiarity was trans- 

 mitted hereditarily in subsequent divisions, so that strains were produced 

 in which the individuals were — to a greater or less extent — deprived of 

 kinetonuclei. 



Laveran and Roudsky (1911, 1911 a) appear to have decided how 

 the kinetonucleus is removed. They have found that when oxazin' is 

 injected into a mouse infected with Trypanosomes, the kinetonuclei of 

 the latter are stained pink or violet with the dye. The rest of the 

 Trypanosome is uncoloured, and it remains actively motile — provided 

 that the dye is not present in such concentration as to kill. The action 

 of the dye can be observed in a drop of infected mouse's blood under 

 the microscope. It seems certain, therefore, that the dye has a special 

 affinity for the kinetonucleus. It can be seen further that the kineto- 

 nuclei which have been stained by the dye — in the living Trypanosomes 

 — dwindle in size, and finally disappear. Laveran and Roudsky ac- 

 cordingly believe that the dyes used have a direct and specific action 

 * Similar results were obtained with acridin. 



15— a 



