2 55 
VI. ANIMAL REACTIONS OF THE TRYPANOSOMES 
(a) Trypanosomes of cattle 
The slight infectivity for laboratory animals of the trypanosomes 
in the majority of the cattle found infected is very striking. It is only 
at Roraee that experimental inoculations were at all successful. No 
morphological variation in the parasites was noted to accompany this 
difference in virulence. All the parasites seen agree with the types 
already described. The results of inoculation of various laboratory 
animals with the trypanosome obtained from Yolo , Steer 9 at Kasongo 
through rat (Exp. 133) are briefly given. 
Monkeys (2). 
Two monkeys, a Macacus rhesus and a Cercofithecus sp ? were inoculated 
intraperitoneal ly with small quantities of infected blood (o'5 and 2 c. cm. respec¬ 
tively). Trypanosomes were never seen in the Macacus , although it was carefully 
eiamined every day. It died 72 days after inoculation, from general tuberculosis. 
Parasites were found in the Cercofithecus on the second day after, but were only 
present in the peripheral circulation for two days ; they then disappeared and were 
never seen up to the time of the monkey’s death, some six weeks after inoculation. 
The monkey had a rise in temperature to 104 0 F. while trypanosomes were present 
in the blood, but afterwards did not have a recurrence of the fever. A rat was 
subinoculated from this monkey on the day of its death with 11 c.cm. of almost 
pure blood, but has not become infected up to the present, 80 days after inoculation. 
Rabbits (3). 
The incubation period varies considerably, from four to sixty-nine 
flays, the usual time being about three weeks. The disease tends to 
he very chronic in these animals, as is strikingly exemplified by the 
Mowing experiment: - 
A rabbit was inoculated subcutaneously on May 3, 1906, with 4 c.cm. of 
™«ted blood and became infected 25 days later. The trypanosomes were present 
ln icant y numbers for a week and then disappeared from the peripheral blood. 
lnce June 4, 1906, they have never been seen, although the rabbit has been un er 
continuous observation. On July 31, two rats were sub-inoculated from the rabbit, 
and bo* became infected after an incubation period of between two and three 
On November 12, 1906, another rat was sub-inoculated from the rabbit 
became infected two weeks later. Finally another rat was sub-inoculated on 
'£*** ‘W, and became infected after a prolonged incubation period of 47 
J*". 11 wil1 thus be seen that the blood is still infective after the lapse of eleven 
D 'J?' hs ; 11 is said that unfavourable conditions, as lack of food, render amnia s 
mW 3rly susce Ptible to trypanosomiasis and may cause a declaration of latent 
10n In order to test this hypothesis this rabbit was placed on a very restnc: e 
. hom December 1, , 9 o6, to the middle of February of this year. Dunn Sj b * 
seen IkT* ” Weight from 2 ’ 79 ° 6 rm - to 2 ’°?5 g™- Trypanosomes whe never 
Jan 0arv h K 6 blood > however, and as stated above a rat sub-inoculated at the e 
- , became infected only after a prolonged incubation. The temp 
mai ned normal throughout. 
