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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    2. Place a loopful in a sterile test-tube containing about 20 c.c. of sterile water, and make sure that the loopful is well distributed. 3. Prepare tubes of beer-wort gelatine by adding 5 \ per cent, gelatine to beer-wort, and sterilising in the usual way, in the steam steriliser. 4. Melt the contents of one of these tubes and add a loop- ful from the Yeast-containing water. 5. Pour the contents of the tube into a sterilised Petri- dish. Allow to set then incubate at 20 0 C. or in a warm room. 6. Observe the colonies which develop on the gelatine. They will probably all conform to one or two types. Select one of the commonest kind and transfer a little of it to a drop of water on a slide. Examine microscopi- cally. 7. If microscopic examination shows that that kind of co- lony is made up of Yeast cells, select one of a similar- kind that is fairly large (not less than \ m.m. in chain.), touch it with a sterilised needle and then dip the needle thus infected into a tube containing sterilised beer- wort, or any other sterile fluid or solid in which Yeast will grow. The resulting growth is probably a pure culture as all the individuals making up the culture have probably been derived from a single cell. Exercise 96. Preparation of vnarked cover-glass. Before we can satisfactorily make a pure culture by the dilution method which is usually employed in the fermenta- tion-industries it is necessary to prepare a cover-glass for the purpose by marking it off into little squares by an etching process. 1. Obtain a large square cover-slip and dip it for a moment by its edges into a crucible containing some melted' paraffin-wax. 2. After the paraffin has set, with a ruler and fine needle^.