1813.] Chemical Properties of Animal Fluids. 23 



cient quantity of sulphuric acid, it yielded sulphate of lime ; 

 and the acid liquor being filtered and evaporated, gave a 

 brownish and highly acid syrup, possessing all the properties of 

 malic acid. The portion dissolved in the alcohol was evidently 

 a mixture of nitrate and nitrate of lime. The mixture consisting 

 of undecomposed carbonate of lime, and the insoluble part of 

 the yellow substance, being decomposed by diluted muriatic acid, 

 left a yellow mass perfectly similar to the one which 1 had before 

 decomposed, and possessing, like that substance, the property 

 of reddening litmus paper. It appeared therefore that 1 had 

 merely exchanged the nitric and malic, for the muriatic acid. 



We thus find that fibrin enters into combination as readily with 

 nitric acid, as with the other before-mentioned acids, and that it 

 is capable of forming two combinations, the one containing an 

 excess of acid and having a pale yellow colour, the other neutral 

 and of an orange hue. By digesting fibrin with nitric acid, it 

 undergoes a species of decomposition by which malic acid is 

 formed. This acid in conjunction with the nitric acid combines 

 with the undecomposed fibrin. The fibrin thus united with the 

 two acids is certainly in some degree altered; for its neutral com- 

 bination with nitric acid is insoluble in water, and retains its 

 insolubility and its yellow colour even when the nitric acid has 

 been displaced by muriatic. On the other hand, we have seen 

 that the precipitate thrown down by nitric acid from a solution 

 of fibrin in acetic acid, acquires a yellow tinge ; but that water 

 in depriving it of the excess of acid, renders it gelatinous and 

 again soluble. It follows that the fibrin, which, in the yellow 

 body, performs the office of a saline base to the nitric acid, must 

 be modified in a different manner from what it is in fibrin com- 

 bined with the acids in the soluble combinations. 



The nitric acid, in which the yellow substance has been 

 formed, has a bright yellow colour: it holds in solution a portion 

 of the yellow substance with a quantity of malic acid. Mixed 

 with alkali in excess, it assumes a very dark yellowish brown 

 colour. 



7. In caustic alkali fibrin increases in bulk, becomes trans- 

 parent and gelatinous, and at length is completely dissolved. 

 The solution is yellow with a shade of green. Acids occasion in it 

 a precipitate which gradually becomes confluent. The solution 

 of fibrin in caustic alkali is pre«ipitated by alcohol, which by 

 means of the excess of alkali dissolves a portion of the neutral 

 Combination of fibrin with alkali. If the aqueous alkaline 

 solution be evaporated, a coagulum is formed towards the end of 

 the process, probably in proportion as the alkali becomes car- 

 bonated. The action of alkali upon fibrin produces some altera- 

 tion in it- properties; for the precipitate thrown down by acetic 

 *cid docs not dissolve by an additional quantity of acid. Jiut 



