84 
Trypanosoma lewisi, etc. 
B. Examination of lice from rats infected with T. lewisi. 
In a number of lice taken from rats more or less heavily infected with 
T.lewisi, it was found that active and typical T. lewisi, unchanged in every 
particular, persisted in various parts of the alimentary tract. In a number 
of cases no active trypanosomes were seen, they had disappeared entirely 
from the gut of the louse. The following Table shews the result of these 
observations, + indicating the presence of T. lewisi, — its absence. 
Eat No. 
No. of lice 
examined 
Eesult 
Eat No. 
No. of lice 
examined 
Eesult 
2 
2 
- 
52 
i 
- 
18 
2 
+ in 2 
54 
4 
+ in 1 
29 
6 
- 
57 
15 
+ in 8 
32 
4 
+ in 1 
64 
3 
+ in 3 
36 
1 
- 
65 
13 
+ in 10 
40 
3 
- 
88 
2 
+ in 2 
47 
8 
- 
89 
15 
+ in 11 
48 
2 
+ in 2 
90 
23 
+ in 13 
8 
28 
+ in 5 
8 
76 
+ in 48 
Total 16 rats, 104 liee, 53+ . 
Therefore, 104 lice were examined from 16 rats, all infected with 
T. lewisi, and in 53 unchanged T. lewisi were found. No flagellates were 
seen in the other lice. 
Where the trypanosomes still persisted in lice, they did not appear 
to affect special tracts of the alimentary canal, but they were never seen 
in either the oesophagus or rectum. Sometimes the trypanosomes were 
in the midgut only, sometimes in the hindgut only, in a few cases they 
occurred in the proximal parts of a Malpighian tube. In one stained 
prepai’ation, a few T. lewisi were seen which appeared slightly changed and 
were probably undergoing involution, since they exhibited fragmentation 
of the nucleus and vacuolation of the cytoplasm. Rat 90, from which 
23 lice were collected and examined, was suffering from a very chronic 
trypanosome infection. 
G. Examination of starved lice. 
A few lice were examined after fasting for a variable period. They 
were easily kept alive for 24 hours in a cool place, but they did not 
readily survive 48 hours fasting. 
