C. DOBELL 211 



It seems legitimate to conclude, therefore, that dyes with an ortho- 

 quinoid structure have a specific action upon the Trypanosome kineto- 

 nucleus*. They fix themselves to it in some way, and bring about its 

 disappearance. 



Concerning the Trypanosomes without kinetonuclei there are but 

 a few additional facts of importance to record. These are results of 

 the work of Kudicke (1911 a). He has not found it possible to obtain 

 from the Werbitzki strain — either by drug treatment or transplantation 

 into other animals — a strain in which the kinetonucleus is present 

 once more. (But compare Werbitzki, p. 206, supra.) From certain 

 immunity experiments, he has concluded that the original strain of 

 "nagana ferox" and the Werbitzki strain derived from it, are — as 

 regards immunity reactions — alike. Kudicke has also made some 

 interesting observations on relapse strains of " nagana ferox." He 

 inoculated a mouse with the strain together with trypan-blue^ Four 

 days later, all the Trypanosomes had disappeared from the blood of the 

 mouse. But four days after this, many Trypanosomes were found in 

 the blood — that is, a relapse race arose. Nearly all the individuals of 

 this race were devoid of a kinetonucleus. After passage through a 

 second, and then a third mouse, all the Trypanosomes were without 

 kinetonuclei. They persisted in this condition during 79 subsequent 

 passages. An explanation of this phenomenon was not arrived at, but 

 it seems that something dififerent from what occurs in the case of ortho- 

 quinoid drugs must have happened^ 



It is perhaps of some interest to recall here — in connexion with the 

 experiments just recorded — certain observations which have been made 

 upon some flagellate Protozoa closely related to the Trypanosomes. 

 Several observers have found occasional individuals which have lost 

 their trophonuclei. Hartmann and Prowazek (Arch. Protistenk. X Bd. 

 1907) noted, for example, that 5-day cultures of the kala-azar parasite 

 contain individuals which have lost this organ. Similarly, Flu (ibid. 

 XII Bd. 1908) and Berliner (ibid. XV Bd. 1909) describe the occurrence 

 of individuals with a similar defect in Crithidia melophagia and 



1 Ehrlich has foand that Trypanosomes which have become resistant to orthoqainoid 

 substances are also resistant to arsenic compounds — a very curious phenomenon. He also 

 found, conversely, that races resistant to arsenic are resistant to the orthoquinoid diphenyl- 

 methane derivatives. 



^ Not an orthoquinoid substance, and usually without action upon the kinetonucleus. 



' The relapse race may have been formed by selection — a chance individual with no 

 kinetonucleus having been more resistant to the drug than the normal forms, and having 

 survived the injection and given rise to the new race. 



