244 Dr. W. Yorke. Auto-Agglutination of [Nov. 2, 
The plasma which had been in contact with the red cells at 0° C. had 
almost completely lost its agglutinating action, whilst the other 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 hemagglutinin 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 centrifugalisation 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. The 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. 
The following procedure was adopted :—The serum and plasma were diluted 
with gradually increasing amounts of 0°9-per-cent. NaCl 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. brucet) 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 blood 
which had been allowed to clot in the ice box. 
The sera of the other animals all showed a considerable deficiency in 
agelutinin as compared with that present in the plasma of the same animals. 
When examining the blood for auto-agglutination it was found that 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° and 40° C. ina 
bottle containing a few glass beads. 
Well marked agglutination was frequently observed when the plasma 
obtained in this manner was added to a 5-per-cent. suspension of red cells, 
whilst either a negative or only slightly positive result was obtained with the 
serum derived from blood which had clotted at laboratory temperature or 
in the ice chest. 
Reversibility of the Reaction—In view of the fact that red cells absorb 
agglutinin to a much greater extent at low temperatures and only slightly 
