(322 



VERTEBRATBD ANIMALS. 



novices in the operation, and who are desirous of perfecting 

 themselves in the practice of the easier methods, before attempt- 

 ing the more costly. By M. Doyere, who first devised this 

 method, it Avas simply recommended to throw in saturated solu- 

 tions of the two salts, one after the other; but Dr. Goadby, who 

 has had much experience in the use of it, advises 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 preparations that are to be mounted 

 dry ; but for such as are to be preserved in fluid, it is subject to 

 the disadvantasre 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 suggest- 

 ing 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, difterent coloring substances should be em- 

 ployed. For a white injection, the carbonate of lead (prepared 

 by mixing solutions of acetate of lead and carbonate of soda, 

 and pouring ofi^ the supernatant liquid when the precipitate has 

 fallen) is the best material. ISTo bhce injections can be much recom- 

 mended, as they do not reflect liglit well, so that the vessels filled 

 with them seem almost black ; the best is freshly-precipitated 

 Prussian blue (formed by mixing solutions of persulphate of 

 iron and ferrocyanide of potassium), which, to avoid the altera- 

 tion of its color by the free alkali of the blood, should be 

 triturated with its own weight of oxalic acid and a little water, 

 and the mixture should then be combined with size, in the pro- 

 portion of 146 grains of the former to 4 oz. of the latter. 



485. Injected preparations may be preserved either dry or, in 

 fluid. The former method is well suited to sections of many 



solid organs, in which the disposi- 

 tion of the vessels does not sustain 

 much alteration by drying ; for the 

 colors of the vessels are displayed 

 with greater brilliancy than by any 

 other method, when such slices, 

 after being well dried, are moist- 

 ened with turpentine and mounted 

 in Canada balsam. But for such 

 an injection as that shown in Pig. 

 328, in which the form and dispo- 

 sition of the intestinal villi would 

 be completely altered by drying, it 

 is indispensable that the prepara- 

 tion should be mounted in fluid, in 

 a cell deep enough to prevent any 

 pressure on its surface. Either Goadby's solution or weak spirit 

 answers the purpose very well. 



Fig. 328. 



Vdli of Small Iiilesliiie of Monkey. 



