742 INJECTED PREPARATIONS! OPAQUE INJECTIONS. 



incorporated, after which the mixture should be strained through 

 muslin. — Although no Injections look so well by reflected light as 

 those which are made with Vermilion, yet other colouring substances 

 may be advantageously employed for particular purposes. Thus a 

 bright Yelloiv is given by the yellow Chromate of Lead, which is pre- 

 cipitated when a solution of Acetate of Lead is mixed with a solution 

 of Chromate of Potass ; this is an extremely fine powder, which 

 1 runs ' with great facility in an injection, and has the advantage 

 of being very cheaply prepared. The best method of obtaining it 

 is to dissolve 200 grains of Acetate of Lead and 105 grains of 

 Chromate of Potass in separate quantities of water, to mix these, 

 and then, after the subsidence of the precipitate, to pour-off the 

 supernatant fluid so as to get-rid of the Acetate of Potash which 

 it contains, since this is apt to corrode the walls of the vessels if 

 the preparation be kept moist. The solutions should be mixed 

 cold, and the precipitate should not be allowed to dry before being 

 incorporated with the Size, four ounces of which will be the pro- 

 portion appropriate to the quantity of the colouring-substance 

 produced by the above process. The same materials may be used 

 in such a manner that the decomposition takes-place within the 

 vessels themselves, one of the solutions being thrown-in first, and 

 then the other ; and this process involves so little trouble or ex- 

 pense, that it may be considered the best for those who are novices 

 in the operation, and who are desirous of perfecting themselves in 

 the practice of the easier methods, before attempting the more 

 costly. By M. Doyere, who first devised this method, it was 

 simply recommended to throw-in saturated solutions of the two 

 salts, one after the other ; but Dr. Goadby, who had much experi- 

 ence in the use of it, advised that Gelatine should be employed, in 

 the proportion of 2 oz. dissolved in 8 oz. of water, to 8 oz. of the 

 saturated solutions of each Salt. This method answers very well 

 for the preparations that are to be mounted dry ; but for such as 

 are to be preserved in fluid, it is subject to the disadvantage of 

 retaining in the vessels the solution of Acetate of Potash, which 

 exerts a gradual corrosive action upon them. Dr. Goadby has met 

 this objection, however, by suggesting the substitution of Nitrate 

 for Acetate of Lead ; the resulting Nitrate of Potash having rather 

 a preservative than a corrosive action on the vessels. — When it is 

 desired to inject two or more sets of vessels (as the Arteries, Veins, 

 and Gland-ducts) of the same preparation, different colouring sub- 

 stances should be employed. For a white injection, the Carbonate 

 of Lead (prepared by mixing solutions of Acetate of Lead and 

 Carbonate of Soda, and pouring-off the supernatant liquid when 

 the precipitate has fallen) is the best material. No blue injections 

 can be much recommended, as they do not reflect light well, so that 

 the vessels filled with them seem almost black ; the best is freshly 

 precipitated Prussian Blue (formed by mixing solutions of Persul- 

 phate of Iron and Ferrocyanide of Potassium), which, to avoid the 



