1. Fill the water compartment to the level of the perforated diaphragm, place the lid in position, and light the Bunsen burner. 2. After the water has boiled, allow sufficient time to elapse for steam to replace the air in the sterilising compartment, as shown by the steam issuing in a steady, continuous stream from the tubulure in the lid. 3. Remove the lid, quickly lower the wire basket containing media tubes, etc., into the sterilising compartment until it rests on the diaphragm, and replace the lid. 4. After an interval of twenty minutes in the case of fluid media, or thirty minutes in the case of solid media, take off the lid and remove the basket with its contents. 5. Now, but not before, extinguish the gas. NOTE.--After removing tubes, flasks, etc., from the steam steriliser, they should be at once separated freely in order to prevent moisture condensing upon the cotton-wool plugs and soaking through into the interior of the tubes. This treatment will destroy any vegetative forms of bacteria; during the hours of cooling any spores present will germinate, and the young organisms will be destroyed by repeating the process twenty-four hours later; a third sterilisation after a similar interval makes assurance doubly sure. The method of sterilising by exposure to streaming steam at 100° C. for twenty minutes on each of three consecutive days is termed _discontinuous_ or _intermittent sterilisation_. Exposure to steam at 100° C. for a period of one or two hours, or _continuous sterilisation_, cannot always be depended upon and is therefore not to be recommended.