Researches on Insect Flagellates introduced into Vertebrates. 143 
: An attempt at culture of heart-blood of this mouse on blood- 
agar met with very slight success. Further experiments are in 
progress. 
Experiment 15 (H.B.F.). An adult female mouse, weight 12°5 
grams, was inoculated intraperitoneally with the gut contents of 
two Gerris paludum infected with Crithidia gerridis, flagellates 
chiefly being present. The inoculation material did not contain 
a large number of flagellates. A small sore developed at the site 
of inoculation but rapidly healed. The hair around the inocula- 
tion point came away and a bald patch was thus formed. The 
mouse became thinner than its control. It was killed in extremis 
on the 40th day after inoculation. Its weight was then 10°8 
grams. Blood smears were examined daily. On the 3rd, 4th, 5th, 
9th, 12th, 15th and 20th days after inoculation, oval, non-flagellate 
parasites were observed in the blood. On the 5th day, dividing 
organisms were seen. Intermediate elongating forms were observed 
on the 5th and 8th days, while on the 13th and 20th days, fully 
formed flagellate Crithidia were present in the. blood. The smears 
of organs when examined showed oval non-flagellate forms in the 
heart, liver, spleen and lungs. Elongating parasites occurred more 
especially in the liver, and a few small flagellates were found in 
the liver and heart. 
Experiment 16 (A.P.). An adult female mouse, weight 14 
grams, was inoculated subcutaneously with the gut of a Gerris 
paludum, containing some preflagellates and a few flagellate forms 
of Crithidia gerridis. Blood films were taken daily for a period of. 
over two months, but all were negative. The mouse was then 
killed, but at autopsy no parasites were seen in any of its organs. 
It had increased in weight by 1:2 grams. 
Hapervment 17 (H.B.F.). An adult male mouse was fed with 
the gut of a Gerris paludum containing flagellate and some post- 
flagellate forms of Crithidia gerridis. Blood smears were made 
daily. On the day after feeding, a small, non-flagellate parasite 
was seen in the blood. Similar non-flagellate forms were found 
on the 8th, 11th, 13th, 20th and 30th day after the infective feed. 
Dividing, oval organisms were observed on the 4th and 20th days. 
Crithidia in various stages of elongation occurred in the circulating 
blood on the 7th, 17th, 20th and 26th days, and fully formed 
flagellates showing an undulating membrane and flagellum were 
present on the 12th and 35th days. .The mouse died on the 38th 
day after the infective feed. It had shown weakness, with a 
staggering gait, for some days previously. It weighed 10°75 grams 
at death, the control mouse from the same litter weighing 
12:7 grams. The liver was pale, the spleen brittle and slightly 
enlarged. The liver contained a few non-flagellate parasites, and 
some uninucleate forms were also present, these latter being rare. 
