C. DOBELL 205 



by Werbitzki were chiefly substances belonging to the pyronin, acridin, 

 and oxazin groups (vide infra) — the best results having been obtained 



Fig. C. T. brucei, strain "nagana ferox." (1) Form without kinetonucleus, 

 after treatment with pyronin. (2) Normal form. [From Werbitzki (1910), 

 slightly diagrammatic.] 



with oxazin. The action of the dye upon the Trypanosomes is rapid. 

 In one experiment in which oxazin was injected into a mouse on the 

 second day after infection with the Trypanosomes, the following ob- 

 servations were made : — 



Hours after injection Number of Trypanosomes 



of dye witliout kinetonucleus 



1 — 2 Isolated specimens 



4 10—12 % 



6 25—30 % 



8 40—50 °/o 



10—12 70—80 % 



24 80—90 °/o 



The strain containing about 80% of individuals devoid of a kineto- 

 nucleus, when inoculated into other mice, shows a smaller — but still large 

 — percentage of the modified organisms. By passing this strain through 

 mice 6 — 10 times, however, and treating with oxazin each time, a strain 

 of Trypanosomes in which every individual is devoid of a kinetonucleus 

 has been obtained. This strain remains constant after numerous sub- 

 sequent passages through untreated mice'. 



The Trypanosomes devoid of kinetonuelei are — as regards motility, 

 general appearance and behaviour, etc. — indistinguishable from normal 

 organisms save in this one feature. Their rate of multiplication is, 

 moreover, unchanged. They show, however, a slight difference in 

 resistance. 



' Kudieke (1911 A) reports that one such strain has been passed through 115 mice, 

 without any treatment, and still retains its moi-phological peculiarity unaltered. 

 Joum. of Gen. ii 15 



