WITH THE MICROSCOPE. 93 



The injection penetrates the capillaries without the necessity of 

 applying much force. It does not run out when a section is made 

 for examination, neither do any particles which may escape from the 

 larger vessels divided in making the section, adhere to it and thus 

 render the section obscure. A structure may be well injected with 

 it in the course of a few minutes. 



Specimens prepared in this manner may be preserved in any of 

 the ordinary preservative solutions, or may be dried and mounted in 

 Canada balsam (but I give the preference to glycerine, 100, or 

 glycerine jelly, 106), and they may be examined with the highest 

 magnifying powers. After having tried very many methods of 

 making this preparation I have found the following one to succeed 

 well. For very fine injections the mixture may be diluted by adding 

 three ounces of glycerine. See also part V. 



178. Prussian Blue Fluid. Composition of the usual Prussian 

 blue fluid for making transparent injections. 



Common glycerine ... ... ... ... i ounce. 



Spirits of wine ... ... ... ... i ounce. 



Ferrocyanide of potassium... ... ... 12 grains. 



Tincture or solution of perchloride of iron* i drachm. 



Water ... ... ... ... ... 4 ounces. 



The ferrocyanide of potassium is to be dissolved in one ounce of 

 the water and glycerine, and the tincture of sesquichloride of iron added 

 to another ounce. These solutions should be mixed together very 

 gradually and well shaken in a bottle. The iron being added to the 

 solution of the ferrocyanide of potassium. When thoroughly mixed, 

 the solutions should produce a dark blue mixture, in which no 

 precipitate or flocculi are observable. Next, the spirit and the water 

 are to be added very gradually, the mixture being constantly shaken 

 in a large stoppered bottle. The tincture of perchloride of iron is 

 recommended because it can always be obtained of nearly uniform 

 strength. It is generally called the mitriated tincture of iron, and 

 may be purchased of the druggists. In cases in which a very fine 

 injection is to be made for examination with the highest powers, 

 half the quantity of iron and ferrocyanide of potassium may be used. 



It has been remarked that as the colour of TurnbulVs blue is 

 brighter and is not liable to fade, it is to be preferred to the Prussian 

 blue. The latter does not, however, lose its colour if a little free 



* The Tinctura Ferri Perchloridi and the Liquor Ferri Perchloridi of the British 

 Pharmacopoeia, of 1867, are of the same strength and consist of one part of the 

 strong Liquor Ferri Perchlor. to three parts, by measure, of spirit or water. 



