S 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, pro to- 

 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 

 600 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. 



