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portion, B, which had been placed in the incubator, had retained 
its auto- and iso-agglutinins intact. 
The following observation furnishes additional proof of the 
capacity of erythrocytes to absorb haeinagglutinin in the cold. 
Specimens of the blood of a number of infected animals were 
collected in sterile tubes and placed immediately in the ice chest to 
clot. After six hours the sera were separated from the clots by 
ccntrilegalisation and were examined for auto- and iso-agglutinins. 
In several cases the results were negative, no auto- or iso- 
agglutination being observed. In other instances the red cells were 
found to be clumped to a greater or less degree. J'he amount of 
agglutinin present in these sera was then compared with that 
occurring in the citrated plasma of the same animals which had been 
separated from the red cells at 37° C. 1 'hc following procedure 
was adopted : The serum and plasma were diluted with gradually 
increasing amounts of o - 9 per cent, sodium chloride solution, and 
the degree of dilution observed at which they no longer caused 
complete agglutination of a given volume of the red cell suspension 
in a stated time. 
The results obtained with one of the animals (Rabbit 1035- 
infected with T. brucei) are given in tabular form. It is to be 
observed that there was at least five or six times as much agglutinin 
in the plasma which had been separated from the red cells at 37 C. 
as in the serum obtained from the blood which had been allowed 
to clot in the ice box. 
The sera of the other animals all showed a considerable 
deficiency in agglutinin as compared with that present in the plasma 
of the same animals. 
When examining the blood for auto-agglutination it was found 
diat the strongest reactions were obtained by dropping the blood 
into a very small quantity of warm citrated saline solution, and 
then separating the plasma from the red cells as speedily as possible 
with the centrifuge. A perhaps even more satisfactory method, and 
one in which the dilution of the plasma by the citrate is avoided, 
is to use the defibrinated plasma obtained by shaking the blood at 
a sustained temperature of between 37 0 and 40° C. in a bottle 
containing a few glass beads. 
