W. L. Yakimoff and others 
65 
rise and on the 7th day reached its maximum, 36-6 %, falling on the following 
day to 13*6 %. Further, up to the 28th day the percentage of these elements 
varied between 15-0 % and 30-6 %, in general showing no tendency to fall. 
From the 29th day a distinct tendency to decrease was observed (amplitude 
between 8*3 % and 17-3 %). 
Thus, in the life of these elements three periods are observed: 
First period, decrease in percentage. 
Second period, slight increase, and absence of a tendency toward the 
decrease in percentage. 
Third period, second decrease in percentage. 
The neutrophil polynuclears behave in the opposite manner, being in 
inverse relation to the lymphocytes. Whilst in the first period the curve of 
the lymphocytes falls, that of the polynuclears rises (to 95-6 % on the 3rd 
day); during the second period, whilst the number of lymphocytes increases 
slightly, the percentage of polynuclears falls (fluctuations between 56-6 % 
and 80 %), and although the curve sometimes rises above the average, no 
tendency toward polynucleosis is observed; lastly, during the third period 
(from the 29th day till death) the curve rises abruptly (to 9T6 % on the 
33rd day), and on the day of death the percentage is 87. 
Is the same phenomenon, which Yakimoff noticed in dogs infected with 
Trypanosoma hrucei and T. equinum, observed here: the direct relation of 
the curve of the total number of white blood corpuscles to the curve of poly¬ 
nuclears, and inverse relation to the curve of the lymphocytes? 
During the first 6 days such a phenomenon was observed, but later (from 
the 7th day till the 19th) the opposite was observed; the curve of the total 
number of white blood corpuscles was directly related to the curve of lympho¬ 
cytes, and inversely to the curve of polynuclears; whilst from the 20th day 
onwards the former conditions were re-established. 
As regards the large mononuclears and the transitional forms, during 
infection a decrease in their percentage is observed, and the former sometimes 
even disappear altogether from the blood. 
No eosinophils and mast cells were present previous to infection, but they ap¬ 
peared later, the latter elements in the last two days of the life of the animal. 
The percentage of TiircFs Reizungsformen and myelocytes increases during 
the infection. 
The Arneth index. The Arneth index had the following aspect before infection: 
1-nuclears ... 
81*1 % 
17*0 
1-3 
0-5 
. The mononuclears rose to 90-3 % on the next day after infection. Further, 
up to the death of the animal the curve remained above the initial figure, 
the lowest percentage being 87-5, and the highest 97*5 (on the last day). 
Parasitology xi 5 
