G. H. F. Nuttall 
147 
The red blood corpuscles could still be discerned after 
278 hours at 12° C. 
?122 „ 14° C. 
42 „ 16° C. 
31 „ 20° C. 
8—24 „ 24° C. 
In no instance could the spirochaetes be found in the coelomic fluid 
of the bugs although they were searched for in about § of the bugs 
tabulated in Experiments I—V. 
Experiment VI. 
This consisted in the inoculation of mice with the gut-contents of 
bugs maintained at a temperature of 12° C. after they had fed to 
repletion on the blood of a mouse suffering from infection with Sp. 
duttoni. The bugs fed at the height of the infection. The gut-contents 
of five bugs were used for the inoculation of each mouse, mixed with a 
drop of salt solution immediately before subcutaneous injection. 
Mouse I 
Time when gut- 
contents of bugs were 
injected after bugs had 
fed on spirochaete blood 
21 hours 
Time after inocula¬ 
tion when mouse 
showed first spiro¬ 
chaetes in its blood 
(examined every day) 
24 hours 
Time after 
inoculation when 
the mouse died 
7 days 
„ II 
i—1 
48 „ 
19 „ 
„ III 
95 „ 
168 „ 
28 „ 
„ IV 
100 „ 
168 „ 
Recovered 
„ v 
120 „ 
72 „ 
23 days 
Under ordinary conditions mice inoculated with Sp. duttoni show 
parasites in their blood after 14—20 hrs. They usually die on the 4th 
to 7th day. The sojourn in the bug for 21 hrs. at 12° C. does not seem 
to exert any influence on the spirochaetes, but after 51 hours there is a 
distinct delay with regard to the time when they appear in the blood of 
the mice and also with regard to the time when the mice die. This 
experiment establishes the fact that the spirochaetes survive for 5 days 
in the bug. The delay in their appearance in the blood of the mice may 
be due to the spirochaetes being present in reduced numbers or possibly 
to their having become attenuated. Judgiug from the results of 
Experiments I—VI it is probable that the spirochaetes may be infective 
after a still longer sojourn in the bug at a temperature of 12° C. 
