1910. | Red Blood Cells in Trypanosomiasis. 249 
agglutinin is that it is formed by the animal mechanism as a direct response 
to the stimulus of the pathogenic agent. In the consideration of this 
question it is necessary to inquire whether auto-agglutinin alone is present 
in excess in infected blood or whether we have at the same time a cor- 
responding alteration in the iso- and hetero-agglutinin contents of the serum. 
Mention has already been made of the fact that in every case where the 
serum of an infected animal was found to possess the property of clumping 
its own erythrocytes to a considerable degree, it also agglutinated markedly 
those of other members of the same species. 
It was further observed that the plasma of infected animals frequently 
appeared to agglutinate the red cells of animals belonging to different species 
to a greater extent than normal. The case of human trypanosomiasis already 
referred to presented an excellent example of an increased capacity on the 
part of an infected serum to agglutinate foreign erythrocytes. The serum of 
this case clumped the red corpuscles of rats, guinea-pigs and rabbits in a 
remarkable manner. A few drops of the inactivated serum when added to an 
equal volume of the blood of one of these animals caused intense agglutination 
in a few seconds at room temperature. The action of normal human sera on 
these corpuscles was much slower and did not approach that of the former in 
intensity. 
Experiments were undertaken with the object of comparing quantitatively 
the auto-, iso-, and hetero-agglutinin in the blood of several infected animals . 
with that existing in the blood of normal animals of the same kind. 
Technique-—The method adopted was that previously used for comparing 
the amount of auto- and iso-agelutinin in the defibrinated plasma separated 
from the red cells at 37° C. with that present in the serum obtained from 
blood which had clotted at 0° C. 
Inactivated defibrinated plasma was prepared from normal Rabbit 1 and 
from Rabbit 896 (infected with 7. dimorphon), and a 5 per cent. suspension 
of washed erythrocytes from the following animals: normal Rabbits 1 and 2, 
Rabbit 896 and a normal horse and guinea-pig. 
From the results of this experiment, details of which are given in 
Table IV, and from other observations of the same kind one is led to 
conclude that in the blood of infected animals, in addition to an excess of 
auto-agglutinin, there is also frequently a corresponding increase in iso- and 
hetero-agglutinin. 
The question now arises as to whether these reactions are manifestations 
of the same body or of different specific agglutinins. The procedure 
usually adopted for the solution of problems of this nature is the saturation 
of a portion of the serum by the red cells of one of the varieties in 
