16 
more rapid disappearance of the parasites from the blood, and the ^ 
greater ntimber of deaths among the white rats. 
The agglutinated parasites have a most orderly arrangement in the * 
shape of a rosette, with their posterior ends close around a central j 
point and their flagella at the periphery. Each parasite has its own 
flne undulating motion. t 
AGGLUTINATION. 
i. By immune serum . — Immunity and agglutinating power go hand 
in hand. As in late years agglutination has been proven for so many 
kinds of bacteria by their specific sera, so m'panosomes are found to 
respond in a somewhat similar way to immune serum. , 
Laveran and Mesnil probably made the most complete study of ' 
agglutination. The trypanosome blood which they used was sub- 
jected to defibrination, which of course left the corpuscles and the | 
trypanosomes in the serum. TT e have found that the substitution of i 
clotting for defibrination will show the agglutination to much l>etter ,| 
advantage in the hanging drop, since there will l>e no corpuscles in j| 
the field to obscure aeelutination. The immune blood and the •! 
'w. I , 
trypanosome-bearing blood may be di’awn up into separate fine capil- \ 
laries and allowed to coagulate. The clot is then drawn out at one I 
end of the tube, leaving the clear imm une serum behind in the one | 
case and the clear serum containing trypanosomes in the other ease. ! 
Xow the dilutions can be made just as in the TTidal reaction. We i 
have, however, taken another precaution which Laveran and Mesnil ■ 
did not observe, W e removed all agglutinin from the trypanosome 
serum before starting the tests. We were led to this bv the studv of 
a uto-a sfslutination . 
If we should select for our agglutination tests blood in which auto- | 
agglutination was alreadv noticeable, we would immediately fall into i 
the error of getting agglutination with ever so great a dilution of the 
immune serum, because the trypanosomes were agglutinated l>efore 
we began. Again, if we selected blood in which there was no auto- 
agglutination, but in which there was considerable agglutinin, but 
still not enough to produce an auto-agglutination, we would still be 
in error if we attempted to determine the agglutinating power of an 
immune serum bytesting it on trypanosome-bearing serum which was 
,]ust on the verge of auto-agglutination. We must therefore take 
into consideration one element which does not enter an agglutination 
test on bacteria. The bacterial pure culture has a fived. uniform 
composition, and until we are able to grow tiypanosomes in pure cul- 
ture on artificial media we will have to consider the element of agglu- 
tinin in the serum which contains the parasites. 
Our plan was to draw the trypanosome blood from the rat, allow it 
to coagulate, draw ofi the serum containing the parasites, and dilute 
it with plain distOled water and filter it thi’ough a porcelain filter . 
