dly supply should be kept on hand.
They are prepared from soft-glass tubing of various-sized calibre (the
most generally useful size being 8 mm. diameter) in the following
manner: Hold a 10 cm. length of glass tube by each end, and whilst
rotating it heat the central portion in the Bunsen flame or the blowpipe
blast-flame until the glass is red hot and soft. Now remove it from the
flame and steadily pull the ends apart, so drawing the heated portion
out into a roomy capillary tube; break the capillary portion at its
centre, seal the broken ends in the flame, and round off the edges of
the open end of each pipette. A loose plug of cotton-wool in the open
mouth completes the capillary pipette. After a number have been
prepared, they are sterilised and stored in batches, either in metal
cases similar to those used for the graduated pipettes or in large-sized
test-tubes--sealed ends downward and plugged ends toward the mouth of
the case.

[Illustration: FIG. 13.--Capillary pipettes. a, b, c.]

The filling and emptying of the capillary pipette is most satisfactorily
accomplished by slipping a small rubber teat (similar to that on a
baby's feeding bottle but _not perforated_) on the upper end, after
cutting or snapping off the sealed point of the capillary portion. If
pressure is now exerted upon the elastic bulb by a finger and thumb
whilst the capillary end is below the surface of the fluid to be taken
up, some of the contained air will be driven out, and subsequent
relaxation of that pressure (resulting in the formation of a partial
vacuum) will cause the fluid to ascend the capillary tube. Subsequent
compression of the bulb will naturally result in the complete expulsion
of the fluid from the pipette (Fig. 14).

[Illustration: FIG. 14.--Filling the capillary teat-pipette.]

A modification of this pipette, in which a constriction or short length
of capillary tube is introduced just below the plugged mouth (Fig. 13,
b), will also be found extremely useful in the collection and storage
of morbid exudations.

A third form, where the capillary portion is about 4 or 5 cm. long and
only forms a small fraction of the entire length of the pipette (Fig.
13, c), will also be found useful.

~"Blood" Pipettes~ (Fig 15).--Special pipettes for the collection of
fairly large quantities of blood (as suggested by Pakes) should also be
prepared. These are made from _soft_ glass tubing of 1 cm. bore, in a
similar manner to the Pasteur