. Public health laboratory work, including methods employed in bacteriological research, with special reference to the examination of air, water and food contributed . e and to allay the dust in sweeping. Direct action of flame.—This simple method ismade use of every day in the bacteriological laboratory, tosterilise the platinum needle employed in making cul-tures, &c. It is to be observed that the needle shouldbe held vertically so that the portion of the glass rodto which the needle is fused is sterilised at the sametime (see later). Pipettes, ampullae and narrow glasstubing may be readily
. Public health laboratory work, including methods employed in bacteriological research, with special reference to the examination of air, water and food contributed . e and to allay the dust in sweeping. Direct action of flame.—This simple method ismade use of every day in the bacteriological laboratory, tosterilise the platinum needle employed in making cul-tures, &c. It is to be observed that the needle shouldbe held vertically so that the portion of the glass rodto which the needle is fused is sterilised at the sametime (see later). Pipettes, ampullae and narrow glasstubing may be readily sterilised by passing quicklythrough the flame. It is unnecessary to point out thatburning is the most efficacious means of getting rid ofall refuse. Hot air.— Hot air is a very useful method of sterilis-ing glass, metal work and cotton-wool. The hot air STERILISATION. 427 chamber is a simple and cheap form of iron oven (). It is furnished with a thermometer and heated bya Bunsen. A temperature of 170° C. is perhaps themost serviceable heat for most purposes, and main-tained for from ten to fifteen minutes effectually steril-ises most apparatus.*. Fig. g8.—The hot air oven. Boiling.—Boiling, or subjecting to steam for fromten minutes to half an hour, sterilises many are very numerous forms of steam 99 represents the well known steam steriliserof Koch. * In sterilisation allowance must naturally be made for the thick-ness and conductivity of the object to be sterilised. The surgeonfor instance is satisfied w^ith boiling his instruments for ten minutes,but insists on several hours for the ligatures. 428 LABORATORY WORK. The principle of this apparatus is that of the or-dinary kitchen steamer, and many of the American
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