370 Maugham.—Observations on the Osazone Method 
undue access of air. When solution is fairly complete this reagent should 
be warmed and filtered at least once. 
Examined under a microscope, the liquid should be nearly free from 
brown particles or drops of phenylhydrazine hydrochloride . 1 It should be 
kept in a darkened bottle preferably having a glass rod attached to the 
stopper for the withdrawal of drops. 
For use, small quantities of the reagents are mixed on a slide, and the 
plant material is placed in the mixture, covered with a glass slip, and then 
heated in a water-jacketed oven for any desired time. 
The preparation is then ready for examination, and provided that the 
material is not directly exposed to air by an insufficiency of the reagent, or 
other cause, nothing more need be done to the slide for some weeks. 
It is very important to keep the tissues properly covered with the 
reagent, as otherwise brown oxidation products form. 
Subsequently the sections may be removed, rinsed in cold water or 
dilute glycerine, and remounted in pure glycerine, the preparation then 
being sealed with a mixture of gum mastic and paraffin wax applied with 
a hot wire . 2 
If air bubbles are present in the tissues they can often be removed by 
an air-pump when the sections are in water or dilute glycerine. 
Except when thick the sections generally become moderately clear in 
pure glycerine. If, however, it is desired to clear them further, weak KOH 
(2 per cent.) may be employed, after which the material should be well 
rinsed in water, or water to which a drop or two of acetic acid has been 
added. 
Staining with aqueous stains can to a certain extent be carried out 
after the above treatment, but this is liable to decrease the transparency of 
the sections considerably. It is preferable to work with unstained material 
once familiarity has been gained with the structure of the tissues under 
investigation. 
Strong glycerine produces some plasmolysis, but in practice this does 
not constitute a serious difficulty. 
Diffusion. 
To a certain extent diffusion of cell contents follows the application of 
the hot reagent, but the amount of this diffusion is less than that which 
occurs with aqueous reagents such as Fehling’s solution. 
In a section several cells thick the contents of the more deeply seated 
1 Such syrupy drops, if present in quantity, resemble the osazone syrup given by maltose (see 
below). Syrup found inside intact cells after treatment with the reagent could, however, hardly 
consist of small particles of phenylhydrazine hydrochloride, as these would have been filtered out by 
the cell membranes. 
2 Cf. Thomas (’ll). 
