1910. | Red Blood Cells in Trypanosomiasis. 241 
exhibited the most marked auto-agglutination of the red cells gave invariably 
negative results when examined for auto- and iso-agglutinins by this method. 
Later it was observed that when the blood from one of the infected animals 
was allowed to flow from a vein of the ear into a watch-glass containing 
a small amount of citrated saline solution, the red cells quickly sank to the 
bottom in little clumps, producing in a marked degree the sandy appearance 
described by Dutton and Todd.* When, however, the watch-glass and salt 
solution were warmed to 37° C. and the blood dropped in as previously, this 
appearance did not result; the red cells remained suspended for a consider- 
able time and only subsided gradually, as in the case of normal blood. So 
long as the temperature of the watch-glass and salt solution was kept at. 
37° C., no agglutination resulted, but as soon as the temperature was allowed 
to fall to about 18° C., the red cells ran together into clumps and the typical 
sandy appearance was obtained. 
These observations served to indicate that temperature played an important 
rdle in the development of the phenomenon. Accordingly, the previous 
experiment was repeated, but on this occasion three sets of tests were made : 
the first were placed in the incubator at 37° C., the second were left at 
laboratory temperature (18° to 21° C.), the last were kept in the ice chest at 
0° C. Even at the end of five minutes a certain degree of agglutination of 
the red cells was noticeable in some of the tubes which had been placed in 
the ice chest, whilst in 15 minutes the red cells in most of them were 
completely agglutinated, numerous clumps of various sizes being visible in 
the clear serum. The reaction was also distinct in many of the tubes kept 
at the laboratory temperature, but it was neither so marked, nor did it occur 
so quickly as in those subjected to the lower temperature. As before, no 
agglutination—or only occasionally a trace—was observable in the tests 
which had been placed in the incubator at 37° C. 
A large number of similar experiments were subsequently performed with 
the blood of monkeys, donkeys, goats, dogs, rabbits, guinea-pigs, and rats 
infected with various strains of trypanosomes. As a rule, it was found that 
a marked degree of agglutination only resulted when the temperature of the 
mixture of serum and red cells was lowered. Very exceptionally slight 
traces of agglutination were also seen in the tests carried out at 37° C., but 
these could not be compared with the intensity of the reaction at low tem- 
peratures. , 
Quite frequently a well-marked auto-agglutination was found to occur, at 
0° C., in the control tests made with the blood of normal animals. I shall 
return to this important point later. 
* Loe. cit. 
