W. L. Yakimoff and others 45 
Mouse No. 87. Inoculated intraperitoneally with infected blood from a calf on Nov. 12 
(trypanosomes absent). 
Nov. 13-Dec. 2 =0. 
Dec. 3 = (+ v.f.)*. 
„ 4-10 = 0. 
„ 11,12=+f. 
„ 13-15=+. 
,, 16 = + +. 
,, 17—20 = + + +. 
,, 20—21 = + + + +. 
Dec. 22 died. Spleen greatly enlarged. 
* v.f. = very few; f. = few. 
Later both the period of incubation and the duration of the disease have 
shortened. On inoculating into the peritoneal cavity the period of incubation 
lasts as follows: 
Bokhara strain 
3-4 days 
Termezh ,, 
3-5 
Samarkand ,, 
5-9 
mlation: 
Bokhara strain 
5 days 
Termezh ,, 
4 
It is easily seen that in cases where the trypanosomes in the inoculated 
fluid are more numerous, the incubation period is shorter; if they are fewer, 
or invisible, this period is prolonged. 
Death occurred 6-9 (in one instance 11, and in another 13) days after 
intraperitoneal inoculation, and 8 days after subcutaneous inoculation; and 
after the appearance of trypanosomes in the blood: 2-5 (and once 10) days 
after intraperitoneal, and 3-4 days after subcutaneous inoculation. 
However we succeeded in invigorating our virus, so that the incubation 
period was reduced to 1 day, and death occurred 1-6 days after inoculation, 
and 3-5 days after the appearance of trypanosomes in the blood. At first, 
even after intraperitoneal inoculation, the period of incubation was 2 days, 
but later it did not exceed 1 day even after subcutaneous inoculation. Inocu¬ 
lation was always (except in mice Nos. 214, 220 and 227) performed with 
such a mixture of the trypanosomes in citrate, that each field of the micro¬ 
scope (Leitz, oc. 4, obj. 7) contained 1 trypanosome. 
With the exception of the cases noted above, the parasites in mice multi¬ 
plied incessantly to the maximum degree + ++ +. 
No clinical phenomena were observable in mice infected with this trypa¬ 
nosome. The alterations in blood are dealt with on p. 69. 
( b ) Rats. When our virus had not yet become acclimatised in the labora¬ 
tory animals, the inoculation of white rats produced the same results as in 
white mice. But later, when it was invigorated, the period of incubation 
