124 



THE MICROSCOPE. 



The iron 'being added to the solution of the ferrocyanide of 

 potassium. When thoroughly mixed, these solutions should 

 produce a dark blue mixture, in which no precipitate or 

 flocculi are observable. Next, the naphtha is to be mixed 

 with the spirit, and the glycerine and the remaining two 

 ounces of the water added. This colourless fluid is, lastly, 

 to be slowly mixed with the Prussian blue, the whole being 

 well shaken in a large bottle during the admixture. The 

 tincture of sesquichloride of iron is recommended because 

 it can always be obtained of uniform strength. It is 

 generally called the muriated tincture of iron, and may 

 always be purchased of druggists. 



" Permit me, then, most earnestly to recommend all who 

 are fond of injecting, to employ transparent injections, and 

 to endeavour, by trying various transparent colouring 

 matters, to discover several which may be employed for 

 the purpose ; for I feel sure that by the use of carefully 

 prepared transparent injections, many new points in the 

 anatomy of tissues will be made out. 



" Of Injecting Different Systems of Vessels with Different 

 Colours. It is often desirable to inject different systems 

 of vessels distributed to a part with different colours, in 

 order to ascertain the arrangement of each set of vessels 

 and their relation to each other. A portion of the gall- 

 bladder in which the veins have been injected with white 

 lead, and the arteries with vermilion forms a beautiful 

 preparation. Each artery, even to its smallest branches, 

 is seen to be accompanied by two small veins, one lying 

 on either side of it. 



"In this injection of the liver, four sets of tubes have 

 been injected as follows : The artery with vermilion, the 

 portal vein with white lead, the duct with Prussian blue, 

 and the hepatic vein with lake. There are many opaque 

 colouring matters which may be employed for double 

 injections, but I am acquainted with very few transparent 

 ones, the employment of which affords very satisfactory 

 results. 



" Mercurial Injections are not much used for micro- 

 scopical purposes, although mercury was much employed 

 formerly for injecting lymphatic vessels and the ducts of 

 glandular organs. The pressure of the column of mercury 



