5. Lift up the bulb by the long capillary stem and allow the mercury to return to its original position--an operation which will be facilitated by snapping off the hair-like extremity from the long piece of capillary tubing. 6. Mark on the capillary stem with a grease pencil the position of the end of the column of mercury (Fig. 19, E.) 7. Warm the capillary tubing at this spot in the peep flame of the Bunsen burner, and draw it out very slightly so that when cut at this position a pointed extremity will be obtained. 8. With a glass-cutting knife cut the capillary tube through at the point "b," and allow the mercury to run out. 9. Now apply a thick layer of sealing wax to the neck of the bulb. 10. Take a piece of 5 mm. bore glass tubing and draw it out as if making an ordinary Pasteur pipette. 11. Break the capillary portion off so as to leave a covering tube similar to that already used for the smaller graduated pipettes. Into this covering tube drop the graduated bulb and draw the capillary stem down through the conical extremity until further progress is stopped by the layer of sealing wax. 12. Warm the pipette in the gas flame so as to melt the sealing wax and make an air-tight joint. 13. Fit an india-rubber teat over the open end of the covering tube, and the automatic pipette is ready for use (Fig. 19, F). ~Sedimentation Pipettes~ (Fig. 20).--These are prepared from 10 cm. lengths of narrow glass tubing by sealing one extremity, blowing a small bulb at the centre, and plugging the open end with cotton-wool; after sterilisation the open end is provided with a short piece of rubber tubing and a glass mouthpiece. When it is necessary to observe sedimentation reactions in very small quantities of fluid, these tubes will be found much more convenient than the 5 by 0.5 cm. test-tubes previously mentioned. [Illustration: FIG. 20.--Sedimentation pipette.] Pasteur pipettes fitted with india-rubber teats will also be found useful for sedimentation tests when dealing with minute quantities of serum, etc. [Illustration: FIG. 21.--Fermentation tubes.] ~Fermentation Tubes~ (Fig. 21).--These are used for the collection and analysis of the gases liberated from the media during the growth of some varieties of bacteria and may be either plain (a) or graduated (b). A simple form (Fig. 21, c) may be made from 14 cm. lengths of soft glass tubing of 1.5 cm. diameter. The Bunsen flame is applied to a spot some 5 cm. from one end of such a piece of tubing and the tube slightly drawn out to form a constriction, the constricted part is bent in the bat's-wing flame, to an acute angle, and the open extremity of the long arm sealed off in the blowpipe flame. The open end of the short arm is rounded off and then plugged with cotton-wool, and the tube is ready for sterilisation. CLEANING OF GLASS APPARATUS.