258 <Auto-Agglutenation of Red Blood Cells in Trypanosonuasts. 
Auto-agelutinin 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. 
This 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. 
