238 THE MICROSCOPE. 



colouring matters used for making transparent injections 

 are carmine and Prussian blue. The former is prepared 

 by adding a little solution of ammonia (liquor ammoniae) 

 to the carmine, and diluting the mixture until the proper 

 colour is obtained, or it may be diluted with size. 



" The Prussian Blue consists of an insoluble precipitate, 

 so minutely divided, that it appears like a solution to the 

 eye. The particles of freshly prepared Prussian blue are 

 very much smaller than those of any of the colouring 

 matters employed for making opaque injections. 



"Advantages of Employing Prussian Blue. I have lately 

 been employing Prussian blue very much, and according 

 to my experience it possesses advantages over every other 

 colouring matter. It is inexpensive, may be injected 

 cold, the preparation does not require to be warmed, 

 no size is required it 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 pre- 

 servative solutions, or may be dried and mounted in Canada 

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

 jelly,) and they may be examined with the highest magni- 

 fying powers. After having tried very many methods of 

 making this preparation I have found the following one to 

 succeed best. 



" Composition of the Prussian Blue Fluid for Making 

 Transparent Injections : 



Glycerine . . . 1 oz. 



Wood, naphtha, or pyroacetic spirit . . . 1| drachms. 



Spirits of wine 1 oz. 



Ferrocyanide of potassium 12 grs. 



Tincture of sesquichloride of iron ... 1 drachm. 

 Water 4 ozs. 



" The ferrocyauide of potassium is to be dissolved in one 

 ounce of the water, 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. 



