Fermentation organisms : a laboratory handbook / by Alb. Klöcker; translated from the german by G. E. Allan and J. H. Millar.

Date:
1903
Catalogue details

Licence: In copyright

Credit: Fermentation organisms : a laboratory handbook / by Alb. Klöcker; translated from the german by G. E. Allan and J. H. Millar. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    111/458 (page 87)
    be avoided. These can, however, when formed, ]:>e expelled by a cautious tapping on the cover glass. Yeast cells and moulds are usually examined in the unstained condition. Water-mounted preparations can be kept for some time if the cover glass is sealed round the edge to the glass slip so that no evaporation can take place. A very suitable medium for this purpose is a solution of common sealing wax in spirit, or a melted mixture of vaseline and bees- wax. If it is wished to make really durable preparations, Hantsch’s solution (see p. 92) is added drop by drop to an ordinary preparation in water so that after some time the only li(|uid remaining in the preparation is glycerine, the alcohol and water having evaporated. The gradual addition is necessary so that the form of the cells may not be altered too much by the water-absorbing property of glycerine. Afterwards the edge of the cover glass is sealed either with the above-mentioned sealing wax solu- tion or with asphalt lac. This method is especially suit- able for preparations of yeast cells and moulds. For the preparation of stained bacteria specimens see below. If the latter are to be made permanent they are mostly mounted in Canada balsam. In permanent specimens the cells always lose their natural form to some extent. Removal of Grease from Cover Glasses.—In preparing a microscopical specimen which is to be fixed, hardened and stained, it is necessary to use perfectly clean cover glasses. To obtain these it is not sufficient to clean them in the ordinary way, but means must be employed to remove the thin layer of grease which always adheres to the glass. The cover glass is first laid in some strong mineral acid (hydrochloric or sulphuric), then washed with water and boiled in a soda solution ; it is again washed with distilled water, dried, washed in absolute alcohol and again dried.