Fig. 252.—Iron Box for holding Sterilised Instruments and Glass Plates.
The needles and instruments used must not be passed through a Bunsen burner flame, which is most destructive, but enclosed in a sheet-iron box made for the purpose ([Fig. 252]), and placed in the hot-air steriliser for an hour at 150°C. The box can be opened at the side, and each instrument withdrawn with a pair of sterilised forceps when required for use.
Glass plates are sterilised in the same iron box, and the platinum needles for inoculating nutrient media, examining cultivations, &c., are served in the same manner before being used. The needles consist of two or three inches of platinum wire fixed to the end of a glass rod. Several of these needles should be made by fixing pieces of wire into a glass rod about six inches long. The glass rod must be heated at the extreme end in the flame of a Bunsen burner, or blow-pipe, and the platinum wire held near one extremity with forceps, and fused into the end of the glass rod. Some of these rods should be straight, and some bent, and others provided with a loop, and kept especially ready for inoculating test-tubes of nutrient jelly.
Fig. 253.—Damp Chamber for Plate-cultivations.
Glass Dishes.—Several shallow glass dishes are required for preparing damp chamber cultivations, the upper covers fitting over the under (as in [Fig. 253]), in the centre of which culture-plates are stacked one above the other, and when necessary placed in the incubator.
Apparatus for Incubation and Cultivations in Liquid Media.
Lister’s Flasks.—Lister devised a globe-shaped flask with two necks, a vertical and a lateral one, the lateral being a bent spout, tapering towards the extremity. When the vessel is restored to the erect position after pouring out some of its contents, a drop of liquid remains behind in the end of the nozzle, and thus prevents the regurgitation of air through the spout. A cap of cotton-wool is tied over the orifice, and the residue left in the flask for future use. The vertical neck of the flask is plugged with sterilised cotton-wool in the ordinary way.
