8 PREPARATION AND MOUNTING 
them. In about half an hour they will become transparent, 
and may be mounted in Canada balsam. 
“A peculiar effect is thus obtained. Epithelial and 
glandular cells, muscles, and the walls of vessels show a 
yellowish colour, with reddened nuclei, while the connective 
tissue is not coloured by the picric acid, and only presents 
the carmine colour.” 
Another mode of effecting the above is by adding to a 
saturated and filtered solution of picric .acid in water, a 
strong ammoniacal solution of carmine, drop by drop, until 
neutralization takes place. Sections may be soaked in this - 
solution, more or less dilute, for a sufficient time, and 
treated as in the previous method. 
The other staining agents are:—nitrate of silver, osmic 
acid, chloride of gold, chloride of gold and potassium, proto- 
chloride of palladium. These are to be made into weak 
solutions in distilled water, in which the tissues, in section 
or otherwise, are to be placed, and then exposed to light for 
a sufficient time. 
Leber recommends a mode of staining by Prussian blue, 
as follows:—Immerse the specimen in a weak solution 
of a protosalt of iron for five minutes, more or less, 
according to size or the thinness of the section. Then 
wash and move it to and fro for a few minutes in a 
1 per cent. solution of ferro-cyanide of potassium until it 
assumes an intense and uniform blue colour. Then wash 
in water, soak in alcohol, and mount as usual. The effect 
is that of partial tingeing; the colour penetrates very 
deeply, and the tissue may be subsequently stained with 
iodine, carmine, or fuchsine. This method has been used for 
the cornea of the frog. 
Iodine 1 part, with 3 of iodide of potassium, dissolved in 
500 of water, may be used for tingeing of a brown colour 
animal cells, as well as all amyloid substances, animal or 
vegetable, sulphuric acid being added. 
