3. Place the hanging-drop slide on a piece of blotting paper moistened with 2 per cent. lysol solution and cover it with a small bell glass that has been rinsed out with the same solution and _not dried_. 4. Raise the bell glass slightly and smear sterile vaseline around the rim of the metal cell by means of a sterile spatula of stout platinum wire. 5. Remove a clean cover-slip from the alcohol pot with sterile forceps and burn off the alcohol; again raise the bell glass and place the sterile cover-slip on the blotting paper by the side of the hanging-drop slide. 6. Remove a drop of the broth from the second dilution tube with a large platinum loop; raise the bell glass and deposit the drop on the centre of the cover-slip. Sterilise the loop. 7. Raise the bell glass sufficiently to allow of the cover-slip being grasped with forceps, inverted, and adjusted over the cell of the hanging-drop slide. Remove the bell glass altogether and press the cover-slip firmly on to the cell. 8. Either incubate and examine at definite intervals, or observe continuously with the microscope, using a warm stage if necessary (Fig. 53). (b) ~Solid Media.~--Observing precisely similar technique, a few drops of liquefied gelatine or agar from the second dilution tube may be run over the surface of the sterile cover-slip and a hanging-drop plate cultivation thereby prepared. This method is extremely useful in connection with the study of yeasts, when the circular cell on the hanging-drop slide should be replaced by a rectangular cell some 38 by 19 mm., and the gelatine spread over a cover-slip of similar size. After sealing down the preparation, the upper surface of the cover-slip may be ruled into squares by the aid of the grease pencil or a writing diamond and numbered to facilitate the subsequent identification of the colonies which are observed to develop from solitary germs. ~Hanging-block Culture~ (Hill).-- _Apparatus required_: As for hanging-drop cultivation with the addition of a scalpel. Carry out the method as far as possible under cover of a bell glass, to avoid aerial contamination. 1. Liquefy a tube of nutrient agar (or gelatine) and pour into a Petri dish to the depth of about 4 mm. and allow to set. 2. With a sharp scalpel cut out a block some 8 mm. square, from the entire thickness of the agar layer. 3. Raise the agar block on the blade of the scalpel and transfer it, under side down, to the centre of a sterile slide. 4. Spread a drop of fluid cultivation (or an emulsion of growth from a solid medium) over the upper surface of the agar block as if making a cover-slip film. 5. Place the slide and block covered by the bell glass in the incubator at 37° C. for ten minutes to dry slightly.