4. Case of sterile Petri dishes. 5. Tubes of sterile nutrient media, gelatine (or agar) previously liquefied by heating in the water-bath and cooled to 42°C., otherwise the heat of the medium would destroy many, if not all, of the bacteria introduced. 6. Tube of cultivation to be planted from. 7. Platinum loop. 8. Bunsen burner. 9. Grease pencil. [Illustration: FIG. 121.--Handy form of water-bath for melting tubes of agar and gelatine previous to slanting them; or to making shake cultures or pouring plates.] Method of "Pouring" Plates.-- 1. Place the glass dish on the levelling tripod (Figs. 122, 123); if gelatine plates are to be poured fill the dish with ice water--gelatine solidifies so slowly that it is necessary to hasten the process; if agar is to be used fill with water at 50°C.--agar sets almost immediately at the room temperature and by slightly retarding the process lumpiness is avoided; cover the dish with the square sheet of glass. 2. Place the spirit level on the sheet of glass and by means of the levelling screws adjust the surface of the glass to the horizontal. This leveling is an important matter since the development of a colony is to some extent proportionate to the supply of medium available for its nutrition. Thus in a "smear" on sloped tube culture, the colonies at the upper part of the medium are stunted and small but increase in size and luxuriance of growth the nearer they approach to the bottom of the tube, where there is the greatest depth of medium. [Illustration: FIG. 122.--Plate-levelling stand.] 3. Place three sterile Petri dishes in a row on the surface of the glass plate and number them 1, 2, and 3, from left to right. [Illustration: FIG. 123.--Plate-levelling stand, side view.] 4. Number the previously liquefied tubes of nutrient media 1, 2, and 3. Flame the plugs and see that each plug can be readily removed from the mouth of its tube. 5. Add one loopful of the inoculum to tube No. 1, treating the liquefied medium as bouillon. After replugging, grasp the tube near its mouth by the thumb and first finger of the right hand, and with an even circular movement of the whole arm, diffuse the inoculum throughout the medium; avoid jerky movements, as these cause bubbles of air to form in the medium. [Illustration: FIG. 124.--Mixing emulsion for plates.] The knack of mixing evenly without producing air bubbles, is not always easily acquired, by this method. An alternative plan is to hold the inoculated tube vertically upright between the opposed palms and to rotate it between them by rapid backward and forward movements of the two hands (Fig. 124). [Illustration: FIG. 125.--Pouring plates.] 6. Sterilise the platinum loop, and add two loopfuls of diluted inoculum to tube No. 2, and mix as before. 7. In a similar manner transfer three loopfuls of liquefied medium from tube No. 2 to tube No. 3, and mix thoroughly.