386 PATHOGENIC BACTERIA.

column to which the blood rises can be taken as a proof
of actual variation. It may be true that no two of the
tubes have exactly—absolutely—the same contents, but
when the given precautions are taken the variation will
be so small as to make no significant error in the results
obtained.

The use of the tubes is extremely simple. The ordi-
nary puncture is made in the lobule of the ear or the fin-
ger-tip of the patient, and one end of one of the tubes
touched to the surface of the oozing drop and held there
until the blood ceases to rise in the tube. So little blood
is required that a number of tubes may be filled with the
blood from a single puncture if desired. The blood in
the tube coagulates in a few minutes, and can be allowed
to dry, or be drawn to the central portion of the tube and
sealed in by fusing the ends in a flame if it be desired to
keep it moist.

When the agglutination reaction is to be made the
blood should not be blown out of the tube, as the total
quantity contained is small and a large relative quantity
will remain in the tube. A better method is to crush the
lube in a small crucible or other diminutive vessel and
dissolve its contents directly in the culture.

The proper proportionate amount of culture is meas-
ured with a finely graduated pipette (graduated to thous-
andths of a cubic centimeter), the calculation according
to the standard tube of the writer's experiments being:
dihitioii i : 10 3= 0.153 c.cm. of the culture; dilution
x : 100 = 1.53 c.cm. of the culture; dilution i : 1000 =
15.3 c.cm. of the culture.

The now recognized specific reaction is supposed to
take place in dilutions of i : 50, which would require
0.71 4- c.cm. of the bouillon or diluted agar culture.

The culture is measured into the little crucible, the
blood-containing portion of the capillary tube broken off,
dropped in, and subsequently crushed to minute frag-
ments and stirred about with a clean, rounded, glass rod,
and a drop of the mixture placed as a "hanging drop"