690 SCIENCE PROGRESS 



arise merely by the selective elimination of the bi-nuclear forms. 

 This explanation, however, is proved to be erroneous by the 

 fact that it is possible to cause the disappearance of the kineto- 

 nucleus in trypanosomes that have ceased to multiply. For 

 example, when T. lewisi has reached the chronic stage of infec- 

 tion in the rat, all multiplication ceases and yet it is possible by 

 appropriate drug treatment to cause the disappearance of the 

 kineto-nuclei from these parasites. The drug is thus shown to 

 act directly upon the kineto-nucleus and not by any process of 

 selection ; it is extremely probable that all drug-resistant races 

 of trypanosomes arise in the same manner. 



Laveran and Roudsky : have investigated the mechanism of 

 the disappearance of the kineto-nucleus in trypanosomes that 

 were exposed to the action of oxazine. This compound exercises 

 a selective staining action on the living parasites, the kineto- 

 nucleus being the only part that is coloured. After taking up 

 the stain, the kineto-nucleus gradually diminishes in size and 

 finally disappears, a process which is easily followed under the 

 microscope. The two authors consider that the disappearance 

 is due to the destruction of the nucleus as the result of a 

 process of autoxidation caused by orthoquinonoid compounds. 

 A strong confirmation of their hypothesis is the fact that 

 minute quantities of potassium cyanide — and also other com- 

 pounds possessing its power of preventing oxidation in the 

 tissues — prevented the oxazine either staining the kineto- 

 nucleus or causing its disappearance. 



(b) The Production of Virulent Races of Trypanosomes by 

 Passage through Cold-blooded Animals. 2 — Fellmer, 3 in 1908, was 

 the first to report that the virulence of T. brucei and T lewisi 

 respectively could be altered by passing them through cold- 

 blooded animals. 



The original observations have been considerably extended 

 in two later communications by Wendelstadt and Fellmer, 3 who 

 show that the trypanosomes are not only altered in virulence 



1 Laveran and Roudsky (191 1), "Au sujet de Taction de 1'oxazine (chlorure de 

 triaminophenazoxonium) et de l'akridine (diphenyl methane) sur les trypanosomes," 

 Compt. Rend. Ac. Set. No. 20, pp. 916-9. 



2 It should be added that Wendelstadt and Fellmer's results have not yet been 

 confirmed by other workers. 



3 Wendelstadt and Fellmer (1909), " Einwirkung von Kaltbliiter-passagen 

 auf Nagana- und Lewisi- Trypanosomen," Zeitschr. f. Immunitatsforschnn%, 

 August, pp. 422-432. 



