WIDAL’S METHOD. gi 
will take advantage of the fact that the platinum loop 
if dipped into a fluid and pressed against a surface so 
that every part of the loop touches that surface will 
deposit a drop of fluid of definite size. You are about 
to mix one loopful of the serum with twenty-nine loop- 
fuls of the emulsion just prepared and examined. 
Blow the blood from the pipette out on to a watch- 
glass (to do this it will be necessary to break the tip of 
the pipette) and tilt the latter so that the serum flows 
away from the coagulum. Now take a loopful of the 
serum and place it on another watch-glass, taking care 
to put the loop flat on the surface of the glass; this is 
done more easily if the wire is slightly bent, or if a flat 
slide is used instead of the watch-glass. 
Next heat the platinum loop in the flame; this is to 
burn off any blood which might remain on it and con- 
taminate the emulsion. Take up a loopful of the emul- 
sion and place it on the watch-glass by the side of the 
drop of serum, but not touching it. Repeat this until 
you have placed twenty-nine drops of emulsion round 
the serum. Mix the whole together by stirring them 
thoroughly with the platinum loop, place a droplet of 
the mixture on a clean cover-glass, and make a hanging- 
drop specimen and examine as before. 
If the blood comes from a case of typhoid fever (with 
certain restrictions which will be discussed below) the 
microscopic appearances will be quite different from 
those seen in the drop of emulsion which was previously 
examined. The bacilli will no longer swim about 
rapidly in all directions; they will become paralysed, 
and remain quite motionless. Further, they will col- 
lect into clumps ; each clump consisting of a larger or 
smaller number of bacilli arranged in a felted net- 
work resembling that seen in a heap of “ spellicans”’ 
