208 Mutation in Micro-On/anisms 



upon the kinetonucleus, which they attack and finally remove. They 

 suggest further that the actual destruction of the kinetonucleus is 

 brought about by autoxidation in situ. Certain experiments appear 

 to support this view. It is known that potassium cyanide and alka- 

 loids — when present in very small quantities — retard autoxidation 

 processes in the tissues. Laveran and Roudsky made a number of 

 different preparations of heavily infected mouse blood. To some they 

 added oxazin alone : to others oxazin with minute quantities of KCN 

 or certain alkaloids'. The results were very striking. Oxazin alone 

 coloured and removed the kinetonuclei of tiie Trypanosomes (as usual): 

 oxazin + KCN, or oxazin + alkaloid, did not affect the kinetonuclei, 

 which remained quite colourless. 



It appears certain, from the above observations of Laveran and 

 Roudsky, that the production of a race of Trypanosomes devoid of 

 kinetonuclei by the action of dye-stuffs, is due to the specific action 

 of the dye upon the kinetonucleus. The latter is attacked by the dye — 

 as is shown by its becoming coloured — and then removed, probably by 

 autoxidation. Laveran and Roudsky find no evidence to show that 

 the kinetonucleus is ever removed by an irregular division — as sug- 

 gested by Werbitzki and Kudicke. They suggest that " if in certain 

 cases the kinetonucleus does not divide at the moment of bipartition, 

 it is probably because it is already dead or altered" — through the action 

 of the dye. 



Werbitzki (1910) found that the only difference — save as regards 

 the nuclei — between his strain and normal 2\ brucei was that the 

 former was less resistant to pyronin. Laveran (1911, 1911a) and 

 Laveran and Roudsky (1911) found that the two strains differed in 

 that the Werbitzki strain had an attenuated virulence for laboratory 

 animals. They also found that injections of oxazin caused the appear- 

 ance of giant forms of the Trypanosomes in infected mice (T. hrucei, 

 T. evansi, T. soudanense). All the species of Trypanosomes without 

 kinetonuclei appear to possess a diminished virulence. 



Laveran and Roudsky (1911 A), by imitating Werbitzki's procedure, 

 have now obtained by oxazin injections a strain of T. evansi which has 

 no kinetonuclei and is apparently fixed in this respect. It breeds true 

 in untreated mice. From T. soudanense, however, they have only suc- 

 ceeded in obtaining a race which — at the 50th passage — contains 66 % 

 of individuals without kinetonuclei. 



' The authors Jo not state which alkaloids they used. 



