CHEMISTRY. 



133 





.cal centrated by evaporation does its solution assume the 



Kiamina- f orm Q f a jelly. 



5. It is not precipitated by the oxymuriate of mcr- 



'li -""'' cury, nor ^7 e " 1 ' us ' on f g a "s- 



6. The acetate ol lead occasions a copious white pre- 

 cipitate when dropt into solutions containing mucus; the 

 superacetate produces a much less striking effect. 



7. Nitrate of silver likewise occasions a precipitate in 

 solutions containing mucus. 



8. When heated, it assumes the appearance of horn, 

 and when distilled it yields the common products of ani- 

 mal substances. According to Fourcroy and Vauque- 

 lin, horn, nails, hair, feathers, the epidermis, and the 

 scales which form on the skir., consist chiefly of mucus. 



,.y of the substances called mucus have the proper- 

 ty of absorbing oxygen, and of becoming by that mearvs 

 insoluble in water. They resemble vegetable extractive 

 matter in this respect. 



SECT. IV. Fibrin. 



Fibrin. If a quantity of blood, newly drawn from an animal, 



be allowed to remain at rest for tome time, a thick red 

 How ah- c ' ot gradually forms in it, and subsides. Separate this 

 ttined. clot from the rest of the blood, put it into a linen cloth, 

 and wash it repeatedly in water till it ceases to give out 

 any colour or taste to the liquid ; the substance which 

 remains after this process is denominated^'"/?!. It has 

 been long known to physicians under the name of the 

 Jibrous part of the blood, but has not till lately been ac- 

 curately described. 



It may be procured also from the muscles of animala. 

 Mr Hatchett, to whom we are indebted for a very in- 

 teresting set of experiments on this substance, cut a quan- 

 tity of lean beef into small pieces, and macerated it in 

 water for 15 days, changing the water every day, and 

 subjecting the beef to pressure at the same time, in order 

 to squeeze out the water. As the weather was cold, it 

 gave no signs- of putrefaction during this process. TKe 

 shreds of muscle, which amounted to about three pounds, 

 were now boiled for five hours every day, for three weeks, 

 in six quarts of fresh water, which was regularly changed 

 every day. The fibrous part was now pressed, and dried 

 by the heat of a water bath. After this treatment it 

 might be considered as fibrin nearly as pure as it can b* 

 obtained. 



It, proper* Fibrin is of a white colour, has no taste nor smell, and 

 bes. is not soluble in water nor in alcohol. When newly ex- 



tracted from blood, it is soft and clastic, and resembles 

 very much the gluten of vegetables. Its colour deepens 

 very much in drying. That which is extracted from 

 muscle by boiling and maceration has a certain degree of 

 transparency, and is not ductile but brittle. Its colour 

 does not deepen nearly so much as the fibrin from blood. 

 It undergoes no change though kept exposed to the 

 action of air ; neither does it alter speedily though kept 

 covered with water. Mr Hatchett kept a quantity of 

 the fibrin which he had prepared from beef moistened 

 with water during the whole month of April ; it acqui- 

 red a musty but not a putrid smell, neither were the fi- 

 bres reduced to a pulpy mass. Even when kept two 

 months under water, it neither became putrid, nor was 

 converted into the fatty matter obtained by macerating 

 recent muscle. 



When fibiin is exposed to heat, it contracts very sud- 

 denly, and moves like a bit of horn, exhaling at the same 

 time the smeli of burning feathers. In a stronger heat 

 it melts. When exposed to destructive distillation, it 

 .Is water, carbonate of ammonia, a thick heavy fi-tid 



oil, traces of acetic acid, carbonic acid, and carbureted 

 hydrogen gas. 



Acids dissolve fibrin with considerable facility. Sul- 

 phuric acid gives'it a deep brown colour; charcoal is pre- 

 cipitated, and acetic acid formed. Muriatic acid dis- 

 solves it, and forms with it a green-coloured jelly. The 

 acetic, citric, oxalic, and tartaric acids also dissolve it 

 by the assistance of heat ; and the solutions, when con- 

 centrated, assume the appearance of jelly. Alkalies pre- 

 cipitate the fibrin fro:n acids in flakes, soluble in hot 

 water, and resembling gelatine in its properties. 



Diluted nitric acid occasions the separation of a good 

 deal of azotic gas, as was first observed by Berthollet. 

 Mr Hatchett steeped a quantity of fibrin in nitric acid 

 diluted wiih thrice its weight of water for 15 days. The 

 acid acquired a yellow tinge, and possessed all the pro- 

 perties of the nitric solution of albumen. The fibrin 

 thus treated, dissolved in boiling water, and when con- 

 centrated by evaporation, became a gelatinous mass, so- 

 luble in hot water, and precipitated by tan and nitro- 

 muriate of tin, and therefore possessing the properties 

 of gelatine. Ammonia dissolves the greater part of the 

 fibrin after it has been altered by nitric acid. The solu- 

 tion is of a deep orange colour, similar to the solution of 

 albumen treated in the same way. Boiling nitric acid 

 dissolves fibrin, except some fatty matter which swims 

 on the surface. The solution resembles that of albu- 

 men ; except that ammonia throws down a white preci- 

 pitate, consisting chiefly of oxalate of lime; Darin* 

 the solution, prussic acid comes over, and carbonic 

 acid gas mixed with nitrous gas ; a considerable portion 

 of oxalic acid is formed besides the fatty matter which 

 swims. 



The alkalies, while diluted, have but little effect upon 

 fibrin ; but when concentrated potash, or soda is boiled 

 upon it, a complete solution is obtained of a deep brown 

 colour possessing the properties of soap. During the 

 solution ammonia is disengaged. When the solution is 

 saturated with muriatic acid, a precipitate is obtained 

 similar to that from animal soap, except that it sooner 

 becomes hard and soapy when exposed to the air. 



The earths, as far as is known, have little or no actiun 

 on fibrin. Neither has the action of the metallic oxides 

 and salts been examined. 



Fibrin is insoluble in alcohol, ether, and oils. The 

 effect of other re-agents on it has not been examined. 



From the properties above detailed, fibrin appears to 

 be composed of the same constituents as gelatine and al- 

 bumen ; but it contains more carbon and azote, and less 

 oxygen. According to the experiments of Thenard and 

 Gay-Lussac, its constituents are as follows : 

 Carbon 53.300 



Oxygen 19.681 



Hydrogen 7.021 



Azote 19.93* 



Cbemic.'.! 



Examina- 

 tion ol 

 Nature. 



Composi- 

 tion. 



10O 



The close resemblance which it bears to albumen, is 

 very obvious from the experiments of Hatchett, just de- 

 tailed. Nitric acid converts both into gelatine, and al- 

 kalies convert both into a species of nil. Now, as all 

 the soft parts of animals consist of combinations of : 

 three genera, it follows, as Mr Hatchett has observed, 

 that all the soft parts of animals may be either convened 

 into gelatine or animal soap, both substances of the 

 highest importance. 



Fibrin exists only in the blood and the muscles of ani- 

 mals ; but it is a genus which includes as many specie* 

 as there are varieties in the muscles of animals ; and the 



