514 



Messrs. H. G. Plimmer and J. D. Thomson. [July 20. 



Table VI. — Nagana and Surra Eats treated with Atoxyl and Iodipin. Average 

 duration of untreated disease, 5*5 and 6*9 days respectively. 



Disease. 



No. 



Weight. 



Quantity 



of 5 p. c. 



atoxyl. 



Quantity of 

 iodipin. 



Recur- 

 rences. 



Lived. 









grammes. 



c.c. 



c.c. 





days. 







f 1 



275 



4-9 



7 '5 



2 



35 







2 



150 



5-4 



9'5 



5 



71 







3 



150 



1-8 



6-0 







26 





Nagana 



i 4 



195 



1-5 



2-0 







112 



Did not die of disease. 





5 



175 



2-1 



6-0 



2 



23 



Did not die of disease. 





1 6 



275 



4-0 



7'5 







29 



Did not die of disease. 





I? 



175 



4-5 



7-0 



3 



44 







f 8 



i 



175 



1-9 



4-0 







57 



Had eight young towards 

 end of treatment. 





! 9 



195 



1-5 



2-0 







— 



Living 132 days. 





1 10 



195 



1-5 



2-0 







— 



Living 132 days. 





1 ii 



143 



6-6 



12-0 



2 



44 





Surra ... 



U2 



250 



4-1 



4-0 



1 



29 



Did not die of disease. 





1 13 



250 



4-0 



4-0 



2 



24 





• i 



1 14 



215 



4'5 



6-5 







— 



Living 103 days. 





1 i5 



165 



2-9 



4-5 



2 



33 







1 16 



150 



3-3 



6-0 



3 



31 



Did not die of disease. 





Li? 



150 



1-8 



2-5 



1 



20 



Did not die of disease. 



The Production of an Atoxyl-proof Race of Trypanosomes in Rats. 



This phenomenon is of great biological and therapeutical interest, and 

 needs much further research yet, both for its explanation, and its bearing on 

 treatment. 



In certain rats, after treatment with atoxyl, a number of recurrences may 

 take place— we have seen as many as seven ; these recurrences at first yield 

 to treatment with atoxyl, but as the case progresses towards its end, the 

 recurrences occur at shorter and shorter intervals, until one comes to a time 

 when they can be no longer affected by atoxyl. The trypanosomes in this 

 case have, become atoxyl-proof. Ehrlich succeeded in producing an atoxyl- 

 proof strain of Nagana in mice, and we have succeeded in producing atoxyl- 

 proof strains of both Nagana and Surra in rats. One point of importance 

 biologically is that these atoxyl-proof trypanosomes do not lose their 

 resistance to atoxyl on transference into other rats, and we have carried this 

 strain on in Nagana through a series of eight successive rats, and in Surra 

 through a series of six rats without any loss of their atoxyl-proof properties. 

 When treated with atoxyl, even in large doses, multiplication goes on just as 

 rapidly as in untreated animals, and the rats die at the usual time. Our 

 cases have been given atoxyl to test them, and have been then treated with 

 various substances, as set forth in the table below. Of these substances, 



