W. L. Yakimoff and others 63 
But here the question may arise: why do we observe in dogs leucopaenia, 
instead of leucocytosis? This can be explained as follows: 
In the horse the infection bears a sub-chronic character; trypanosomes 
are not always present in the blood, and their number varies between + v.f. 
and only + + . 
In the dog, however, this disease is acute; trypanosomes are always 
present in the blood and in large numbers. 
It is on account of this difference that the organism of the horse struggles 
more successfully against the infection; the leucocytes fighting against the 
parasites pass into the blood in larger numbers than in the dog; therefore, 
they are all the time present in increased numbers, as if “on guard.” In 
dogs, however, the parasites—the foes of the organism—are more powerful 
than its defenders, and the latter are fewer. 
Nevertheless, many leucocytes also perish in the organism of the horse 
(which is seen in the enormous leucocytolysis observed by us) and the 
organism, through its haematogenous organs, is obliged to fill up the defici¬ 
ency in the form of young elements—lymphocytes. 
Now we can understand the reason of such an enormous loss of poly- 
nuclears, hence the “shift to the left” in the Arneth index, and the appearance 
in the blood of the “young” leucocytes—the lymphocytes—and their rapid 
transition into the “mature” (transitional) forms. 
X. CHANGES IN THE BLOOD OF THE DOG DURING INFECTION 
WITH THE CAMEL TRYPANOSOME 1 . 
A dog was inoculated intraperitoneally with a large quantity of blood 
containing trypanosomes and as a result became infected after an incubation 
period of only 4 days. It succumbed on the 35th day. Trypanosomes appeared 
in the blood on the 5th day after infection (+) and after this for three periods: 
from the 8th to the 14th day 
,, 16th ,, 25th ,, 
,, 29th ,, 35th ,, 
the number of trypanosomes varied from + v.f. to + + +. 
The red blood corpuscles which previous to infection numbered 6,048,000 
decreased progressively: 
33 
33 
5th dav after infection there were 
«/ 
6,584,000 
11th ,, • 
33 
33 
5,544,000 
17th 
33 
33 
3,876,000 
21st ,, 
33 
33 
3,496,000 
25th 
33 
33 
3,744,000 
35 th „ 
33 
33 
2,728,000 
By W. L. Yakimoff and R. N. Kohan-Marnier. 
