Practical bacteriology for chemical students / by David Ellis.

  • David Ellis
Date:
1923
Catalogue details

Licence: In copyright

Credit: Practical bacteriology for chemical students / by David Ellis. Source: Wellcome Collection.

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    3. When a surface growth has appeared on the agar, examine a portion microscopically, in a drop of water. [Avoid putting too much Yeast-material in the drop of water. The latter should be barely visibly turbid after the Yeast-material has been added to it.] Make drawings of a few of the Yeast cells, choosing for the purpose as many differently shaped cells as possible. Exercise 91. Preparation af Pasteur’s Fluid. Place 75 grams of pressed Yeast in a vessel containing 1 litre of water, warm until the mixture boils, then allow it to boil for a further hour. Filter. Filtrate should be pale yellow, make it up to one litre with water then sterilise in steam-steriliser, add 5—10 per cent, cane sugar. Exercise 92. Gas-production during Yeast-fermentation. 1. Fit up apparatus shown in Fig. 39. The tube projecting into mouth of flask A, leads outside A into a gas col- lecting apparatus, compos- ed of a fairly wide-tubefull of water and inverted into a basin containing water. The test-tube is held by a clamp so that it can be raised about half an inch or more from the bottom of the basin. This is to allow the tube leading from A to pass into the basin and to be inserted under or slightly inside the col- lecting test-tube. 2. Remove plug from A and pour in Pasteur’s fluid until the flask is half full. [The end of the leading tube must be well above the surface of the Pasteur fluid, when it is replaced in position.] 3. Add a thimbleful of pressed Yeast to every 4- litre of Pasteur fluid. Fig. 39. — Diagrammatic representa- tion of apparatus for collecting samples of gas evolved during Yeast-fermenta- tion. For further explanation see Exercise 92.