A note book for the elements of the comparative anatomy of invertebrates.

Date:
1911
Catalogue details

Licence: In copyright

Credit: A note book for the elements of the comparative anatomy of invertebrates. Source: Wellcome Collection.

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    Hamatoxylin is a powerful nuclear and a selective plasma stain dissolved in about 25 per cent, alcohol. It may be diluted with 50 per cent, alcohol. It is used instead of boraxcarmine, and in the same way, giving a blue colouration. The object must be washed with acid alcohol for 1—2 minutes to remove the superfluous stain. It should then be washed in 70 per cent, alcohol. Picric acid dissolved in alcohol or water is useful for staining chitin (the exoskeleton of Crustacea etc.). It may be used for suitable objects after any of the carmine stains. 3. Mounting in Glycerine. Specimens stained in picrocarmine can, after washing with water, be transferred at once to dilute glycerine and a few minutes afterwards to a drop of pure glycerine on a slide. Care must be taken that too much glycerine is not used. The coverslip is prevented from slipping on the slide by painting a solution of gold size in xylol round the edges of the coverslip. With the evaporation of the xylol the gold size hardens. Only animals or tissues of slight thickness should be mounted in glycerine, for the reagent clears slowly. It must however always be used when the preparation is intended to show objects of high refractive index like spicules or setae. 4. Mounting in Canada Balsam. This is the more permanent method of mounting. It entails the removal of all water from the specimen by passing it through a series of alcohols of graduated strength. In the case of a small object which has already been fixed but not stained, dehydration may be effected by passing the following succession of fluids into the watch glass : 30 per cent, alcohol 3 minutes. 5° 70 ,, ,, 5 minutes. 90 „ „ 5 minutes. Absolute alcohol 5 minutes. The still opaque object is then treated with oil of cloves as a clearing agent, in which it remains till it is entirely transparent. If dehydration is not complete, a milky precipitate is formed in the oil of cloves and the specimen should be returned to absolute alcohol for a few minutes. From oil of cloves the specimen may be transferred to a drop of Canada balsam on a slide and a coverslip then placed on top. The balsam is dissolved in xylol and, as this solvent evaporates, sets hard so that the coverslip remains permanently fixed without employing gold size. The process of evaporation can be accelerated by leaving the slide on a hotwater-bath for a day.