1910. | Red Blood Cells in Trypanosomasis. 255 
The capacity of the untreated plasma of Rabbit 1035 and of the solution 
prepared by digesting the agglutinated red cells with normal saline at 0° C. 
to agglutinate these different erythrocytes was then examined. 
The information obtained from observations of this kind is extremely 
interesting. In the experiment recorded a substance was extracted from the 
auto-agelutinated erythrocytes of a rabbit infected with Z. brucet which 
clumped not only its own erythrocytes and those of other rabbits, but also 
the red cells of many other animals of different species. In other words it 
would appear that the auto-agglutinin is not a body equipped with a high 
degree of specificity, but that it can also act as iso- and hetero-agglutinin on 
the erythrocytes of other rabbits and those of animals of widely different 
species. 
Value of the Phenomenon as a Diagnostic Sign.—Before discussing this 
question it is necessary to emphasise the importance of careful observation 
in determining whether a certain blood really agglutinates or not. So far as 
can be gathered from the papers in which the existence of the phenomenon 
in trypanosomiasis has been recorded, it has been invariably decided from 
the examination of cover-slip preparations of the blood. Although a con- 
siderable degree of auto-agglutination is easily recognised in a well-made 
cover-slip preparation, yet it is often extremely difficult, or even impossible, 
to decide whether the red cells are really agglutinated when the phenomenon 
is not so distinct. A certain amount of massing together of the erythrocytes 
is frequently evident at the edges of even the best cover-slip preparations of 
normal blood, whereas if the slide and cover-slip be not perfectly clean the 
red cells are found to be anything but evenly distributed, but are grouped 
together into little masses and rouleaux, separated from one another by 
plasma—an appearance closely resembling that to be observed in infected 
blood when the amount of auto-agglutination is shght. On the other hand, 
a slight degree of auto-agglutination can be easily obscured by pressure on 
the cover-slip resulting in the separation of the erythrocytes one from the 
other. 
Furthermore, it has been shown that small amounts of auto-agglutinin 
exist constantly in the blood of many normal animals. In horses and 
donkeys auto-agglutinin is sometimes present in such an extent as to give 
rise to a more or less characteristic appearance in cover-slip preparations. 
This is specially the case when the preparations are made out of doors at 
a somewhat low temperature. However, I have never observed in cover-slip 
preparations of the blood of normal animals a condition approaching in 
intensity the well-marked clumping obtaining in infected cases. When 
a high degree of auto-agglutination exists the corpuscles are seen to have 
VOL. LXXXIII.—B. U 
