744 INJECTED PREPARATIONS ! TRANSPARENT INJECTIONS. 



or by immersion in the Chromic acid solution or in Alcohol, thin 

 sections are cut with a sharp razor ; and these are usually dried 

 and mounted in Canada balsam. Many of these Transparent Injec- 

 tions (Plate xxv.) are peculiarly well seen under the Binocular 

 Microscope ; which shows the Capillary network not only in two 

 dimensions (length and breadth), but also in its third dimension, 

 that of its thickness. This is especially interesting in the case of 

 injections of the Nervous Centres. The Stereoscopic effect is best 

 seen, if the light reflected through the object be moderated by a 

 ground-glass or even by a piece of tissue-paper placed behind 

 it. — This method, however, does not serve to display anything 

 well, save the distribution of the Capillary vessels ; the struc- 

 tures which they traverse being so imperfectly shown, that 

 little light is thrown on the relations of the two. For the 

 purpose of scientific research, therefore, the method followed by 

 Dv. Beale (for full details of which the reader is referred to his 

 Treatise) is much to be preferred. The material recommended 

 by him for the finest Injections is prepared as follows : — Mix 

 10 drops of the Tincture of Perchloride of Iron (Pharm. Brit.) 

 with 1 oz. of Glycerine ; and mix 3 grains of Ferrocyanide of 

 Potassium, previously dissolved in a little Water, with another 1 oz. 

 of Glycerine. Add the first solution very gradually to the second, 

 shaking them well together ; and lastly, add 1 oz. of Water, and 

 3 drops of strong Hydrochloric acid. This "Prussian Blue Fluid" 

 is not a solution, the precipitate being only suspended in it ; but 

 it does not deposit the slightest sediment, even when kept for some 

 time ; and it appears like a solution even when examined under 

 high magnifying powers, in consequence of the minuteness of the 

 particles of the colouring matter. Where a second colour is re- 

 quired, a Carmine injection may be used, which is to be prepared 

 as follows :— Mix 5 grains of Carmine with a few drops of Water, 

 and, when they are well incorporated, add about 5 drops of Strong 

 Liquor Ammonia?. To this dark red solution add about \ oz. of 

 Glycerine, shaking the bottle so as to mix the two fluids thoroughly ; 

 and then very gradually pour in another \ oz. of Glycerine acidu- 

 lated with 8 or 10 drops of Acetic or Hydrochloric acid, frequently 

 shaking the bottle. Test the mixture with blue Litmus paper ; 

 and mix with it another £ oz. of Glycerine, to which a few drops 

 more Acid should be added, if the acid reaction of the liquid 

 should not have previously been decided. Finally, add gradually 

 2 drachms of Alcohol previously well mixed with 6 drachms of 

 Water, and incorporate the whole by thorough shaking after the 

 addition of each successive portion. — The Staining Process (§ 145) 

 may be combined with the Injecting ; but Dr. Beale has now come 

 to prefer the following method, when such a combination is desired. 

 An Alkaline Carmine fluid rather stronger than that ordinarily 

 employed (Carmine, 15 grs., Strong Liq. Amnion., 4 drachm, Gly- 

 cerine, 2 oz., Alcohol, 6 drachms) is first to be injected carefully 



