TRYPANOSOME OCCURRING IN THE BLOOD OF MAN 465 
The Identification of the Parasite Found in Man 
It is now known that the course of the disease produced by a trypanosome, 
varies in the different animals experimentally inoculated ; some animals being more 
refractory than others ; and the parasite also varies in its morphological character 
in the different animals, and with regard to the numbers occurring in the blood. 
Laveran and Mesnil' and others have shown that T. kwisi cannot be inoculated 
into the larger animals, dog, cat, cow, horse, mule, etc. It produces no pathological 
effect in rats. Divisional forms are only seen for a short time in the blood, four to 
eight days after inoculation (Laveran and Mesnil), and it can be easily distinguished 
from the other trypanosomes by its morphological characteristics ; thus, comparing 
T. kwisi with T. brucei, the former is smaller and thinner, length measuring 24-25 fi, 
breadth 1*5 while the latter measures 26-27 M length, 1*5 to 2-5 fi breadth in the 
rat. The general aspect of the parasite is finer, the posterior end is pointed, while 
in T. brucei it is blunt. The macro-nucleus is situated at the anterior end of the 
body, the macro-nucleus is placed transversely as a rule and is large (Plimmer and 
Bradford), the protoplasm stains less deeply with basic dyes. In T. brucei the 
macro-nucleus is placed centrally, the macro-nucleus is small, protoplasm stains well, 
and in it are chromatic granules situated anterior to the nucleus (Laveran and 
Mesnil). 
Plimmer and Bradford 2, describe Amoeboid and Plasmodial modes of multi- 
plication as well as longitudinal division in the case of T. brucei, while in the 
T. kwisi longitudinal division is the rule. Laveran and Mesnil' shew that longi- 
tudinal division differs in the two parasites. T. kwisi is more resistent to cold than 
T. brucei. Laveran and Mesnil 3 inoculated rats successfully with blood containing 
T. kwisi after being fifty-five days in the refrigerator at 5-7 0 , they were unsuccessful 
with blood containing T. brucei which had been kept three to five days in the 
refrigerator, although a few motile organisms were present. 
In the case of tsetse trypanosome, Bruce 4 pointed out that the parasite 
differed in appearance in the various animals he inoculated. Plimmer and Bradford, 1 
and Laveran and Mesnil 3 have studied the T. Brucei in the horse, dog, cat, rat, 
mouse, etc. In the rat and mouse the organisms are always numerous and steadily 
increase in the blood until death, which takes place in six to nine days. In the rabbit 
the parasites are only found at irregular intervals ; in the goat the disease is protracted 
(death in two months) and the organisms are not found abundantly in the blood ; the 
spleen is not enlarged. In the horse the parasites were longer and thinner than in 
any other animal. Laveran and Mesnil 3 state that the parasite varied from 28 to 
I. Laveran and Mesnil. Sur le Trypanosome des Rats. Ann. de 1' Institut Pasteur, Sept. 25, 1901. 
2. Plimmer and Bradford. The Trypanosoma Bnicii, the organisms found in Nagana. Shmrterly "Journal, Micro. Society, 
Vol. 4,5, Part v 
3. Laveran and Mesnil. Sur le Trypanosome der Nagana on Maladie de la Mouche Tsetse. Ann. de I' Institut Pasteur, 
Jan. 25, 1902. 
4. Bruce, loco cit. 
