694 SCIENCE PROGRESS 



was again put back into a mouse ; the trypanosomes at once 

 became atoxyl-resistant, showing that this character had been 

 preserved though the parasites had not come into contact with 

 the drug. 



Breinl and Nierenstein l also described an interesting case 

 in which they developed an atoxyl-resistant race of T. equiperdum 

 (dourine) in donkeys. This race was inoculated into white rats 

 and afterwards passed successively through guinea-pigs, rabbits 

 and rats during a period extending over seven months ; when 

 finally a donkey was inoculated, it was found that the race 

 had maintained its resistance to atoxyl after all this time. 



It has since been shown that atoxyl does not act directly 

 on the parasites but only after it has entered into combination 

 with the proteids of the blood. Therefore, when a race has 

 acquired the power of resisting the compound of atoxyl with 

 mouse-proteid, it does not necessarily possess any power of 

 resisting the compound of atoxyl with the serum proteids of 

 another species as the blood of different animals is well known 

 to differ. Consequently, the specific nature of the character of 

 atoxyl-resistance is easily explained. 



The experiments referred to have been described mainly 

 with the object of showing how persistent a character may be 

 in these parasites when once it has been acquired ; and also 

 to show how rapidly such an acquired character as that of drug- 

 resistance may be produced. Finally, we come to the most 

 interesting and important results that have been obtained from a 

 study of this character of drug resistance, viz., those of Gonder. 2 



It had long been a contested point whether or not this 

 character was maintained when the parasites were transmitted 

 by the normal intermediate host. The majority of writers seem 

 to have assumed that it was maintained but no experiments 

 had been made on the subject until Gonder attempted to trans- 

 mit a resistant race of T. lezvisi, the rat trypanosome, by means 

 of the intermediate host Hcematopinus spinulosus, the rat louse. 



The race of rat trypanosomes used was one that had acquired 

 the power of resisting arsenophenylglycin and had retained 

 this character after passage through a large number of rats. 



1 Breinl and Nierenstein (1908), " Weitere Beobachtungen iiber Atoxylfestig- 

 keit der Trypanosomen," Deutsche Med. Wochenschr. vol. xxxiv. pp. 1181-2. 



2 Gonder (191 1), " Untersuchungen iiber arzneifeste Mikroorganismen : I. Try- 

 panosoma lewist" Centralbl.f. Bakteriologze, vol. lxi. pp. 102-113. 



