17 
! under the influence of a vacuum. After four or five washings with 
large amounts of water, we let it filter until there remained behind a 
volume of fluid which equaled the original amount of serum. In this 
i residue were the trypanosomes free from agglutinin. Dilutions were 
then made of the immune serum, and it was tested on the washed 
parasites. Some immune sera will not agglutinate in a dilution 
greater than 1 : 1. An agglutinating power of 1 : 5 or 1 : 10 is common. 
One of our rats showed typical agglutination in a dilution of 1 : 200. 
It is interesting to Avatch in hanging drop an agglutination by a 
weak serum. At first two or three parasites are seen, joined by their 
posterior ends. Others come up toward the center of agglutination, 
! recede for some distance, and later join the others. Some disengage 
I themselves from the rosette and then rejoin it, until finally a Avell- 
i arranged rosette is formed. Two small rosettes will graduall}^ 
j approach each other and then unite to form one mass, which in turn 
|j is joined by others of smaller or larger size. 
A remarkable fact is that the agglutinated jiarasites do not lose 
^1 their motility. There is not the diminution of motility before agglii- 
I tination that is seen in a typhoid reaction, and while agglutinated 
I each parasite retains a regular vibration. In agglutination with a 
I strong serum the process takes place rapidly. The j)arasites rush 
together in great numbers, and the masses may be of macroscot)ic 
size. If a strong specific serum is used, the agglutinated masses are 
' very compact and the individual parasites are tightly drawn together, 
^ so that there is little motion. In a general way the parasites are all 
I pointed toward a center, but still they overlap and cross each other 
very much. With a weak serum the parasites are held together in a 
loose manner, permitting of more individual movement to each organ- 
ism and more orderl}^ arrangement, and there are fewer parasites to 
% each rosette. 
•I We often found agglutination almost complete, in which case A^ery 
I few parasites Avere to be seen free in the field. It may be only par- 
I tial. Th6 parasites may remain agglutinated until their death, or, if 
’ the serum is weak, a disagglutination may follow. Specific sera 
I exposed to 55° C. for thirty minutes did not lose the agglutinating 
( power, but a temperature of 65° C. maintained for half an hour 
. destroyed its activity. 
Laveran and Mesnil found that trypanosomes killed by chloroform 
or formalin were agglutinated by the same sera which agglutinate the 
jiB living, but the parasites have no orderly arrangement in the mass. 
i| It is a remarkable fact that Rabinowitsch and Kempner found that 
‘ ‘ ‘ the trypanosome serum shows in no Avay Avhatever the property of 
agglutination. ” 
2. By normal sera . — The action of normal sera in dilution of 1:1 
was tested on the trypanosomes. The cat and horse sera were 
’ strongly agglutinating. The goat and rabbit sera were feebly agglu- 
20564— No. 11-03-^ — 2 
