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SUMMARY 
Auto- and iso-agglutinin are present in the blood of cases of 
sleeping sickness and of animals infected with trypanosomiasis. 
Reaction between auto-agglutinin and red blood cells takes place 
only at low temperatures. 
Auto-agglutinin can be removed from plasma by absorption with 
the erythrocytes of the same animal at o° C. 
The reaction between auto-agglutinin and red blood cells is 
reversible. 
Auto-agglutinin exists in small amounts in the blood of many 
normal animals. 
Auto-, iso- and hetero-agglutinin are frequently present in much 
greater amount in the blood of infected animals than in that of 
normal animals, and it is due to this fact that clumping of the red 
blood cells is often visible in fresh cover-slip preparations of the 
blood of infected animals. 
From the red blood cells of an infected animal which have been 
agglutinated in the cold by the plasma of the same animal an 
active substance can be extracted with normal saline solution at 
37 ° C. 
1 his substance agglutinates not only the red cells of the same 
animal and other members of the same species, but also those of 
many animals of different species. 
It is to be inferred from the information at present available 
that a marked degree of auto-agglutination of the red blood cells is 
an extremely rare occurrence apart from an infection with 
trypanosomes. 
