86 
Trypanosoma lewisi, etc. 
Therefore 21 out of the 36 lice examined contained T. lewisi in their 
gut. The Table shews that the blood in the gut of the lice shewed 
all degrees of digestion. Whereas some of the lice whose intestine 
contained bright-red blood harboured no trypanosomes (3), the majority 
(14) contained T. lewisi. In lice, where the blood shewed evidence of 
having been more or less digested (19), only 7 contained trypanosomes. 
In these 7 lice, the digestion had proceeded to varying degrees, so that 
the gut-contents appeared dark red in three, dark brown in one, brown 
in one, greenish-brown in one, and straw-coloured in one. 
E. Examination of fleas from rats infected with T. lewisi. 
Taking now the fleas, Gtenophthahnus agyrtes, from infected rats, 
which were examined immediately after their removal from the rats, it 
was found that the trypanosomes could not be seen at all in the great 
majority examined, and that the examination of stained preparations of 
the gut-contents confirmed their absence. 
The subjoined Table shews the result of these observations: 
Eat No. 
No. of fleas 
examined 
Eesult 
18 1 
19 8 
20 5 
21 5 
29 1 
52 9 
53 3 
54 2 
55 6 
56 3 
84 1 
123 1 
+ in 1* * 
+ in 1 
12 45 
* Only one sluggishly moving trypanosome was detected. 
Therefore 45 fleas from 12 rats infected with T. lewisi were examined, 
with the result that in all but two fleas T. lewisi had already disappeared. 
F. Examination of fleas from uninfected rats. 
Of the fleas from uninfected rats, not one shewed any trypanosomes 
in stained or fresh preparations. 
