76 
Insect Flagellates , etc. 
Experiment 10. Young mouse inoculated on September 15th. Found dead on 17th. Not 
examined on account of decomposition. 
Experiment 11. Mouse inoculated on October 26th. Sacrificed next day. Stained smears 
of blood, spleen and liver—negative. Peritoneal fluid showed numerous leucocytes. Blood 
cultures (at 30° C.) remained sterile for 11 days. The animal was in weak condition when 
killed. 
Experiment 12. Young mouse inoculated on September 15th. Sacrificed on the 22nd. 
Blood examination till that date, negative. Smears of organs (as above)—negative. Blood 
cultures (13 days at 24° C.)—negative. 
Experiment 13. Mouse inoculated on September 6th. Sacrificed on the 22nd. Blood 
examination till that date—negative. Smears of organs (as above)—negative. Blood cultures 
(13 days at 24° C.)—negative. For four days the mouse was in a weak condition, but 
recovered later. 
Experiment 14. Mouse inoculated on October 26th. Sacrificed after one month 
(November 26th). Blood examination during that period revealed no parasites. Smears of 
blood, liver, spleen and peritoneal fluid—negative. Blood cultures kept at 24° C. remained 
sterile. 
On the next day after inoculation the mouse was in weak condition, but soon recovered. 
It later developed gangrene on the tail, and examination post mortem showed a suppurative 
nodule in the fiver, which, as I am told, is not uncommon in mice. 
Experiment 15. Mouse inoculated on November 26th. After 3£ hours its blood and 
peritoneal fluid were examined fresh and stained. No parasites were found, but the exudate 
showed numerous leucocytes. The blood was regularly examined for 15 days, but showed no 
parasites. The mouse was sacrificed after 15 days; in smears of its organs no parasites could 
be found. Blood cultures kept at 24° C. remained sterile. 
In the preceding experiments different doses of flagellates were inoculated into the mice. 
Nos. 8, 9, 10 and 12 received the contents of four Nepa guts each; Nos. 11 and 14—two each; 
No. 15—one gut. 
As the experiments on mice show, there was no trace of flagellate infection 
in any of the cases recorded. Blood examinations were made at periods 
ranging from 3J hours to 35 days with the same results. Cultures (at 24° C. 
and 30° C.) from the blood and organs of the infected animals examined in 
some cases for 56 days likewise failed to reveal any parasites. 
B. Experiments with Fish. 
I. Sticklebacks (Gasterosteus aculeatus) fed on the flagellates of Nepa cinerea 
(H. jaculum). 
The contents of the gut of Nepa were examined for flagellates. If present, 
the gut was fed to the fish. It was always eaten immediately after being 
offered. Altogether 11 feeding experiments were conducted (each fish kept 
in a separate jar) varying according to the number of days they were fed, the 
number of Nepa guts they had eaten, and the length of time from the last meal 
to the date when they were sacrificed. For comparison, control fish were 
examined. 
The examination of infected fish was conducted as follows. First the gill 
operculum was removed to expose the heart. Blood was then taken directly 
