FIBRIN. If a quantity of blood, newly drawn from an animal, be allowed to re main at rest for some time, a thick red clot, gradually forms in it, and subsides. Separate this 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 whidh remains after this pro cess is denominated fibrin. It has been long known to physicians, under the name of the fibrous partof the blood ; but has not till lately been accurately describ ed. It may be procured also from the muscles of animals.
Fibrin is of a white colour, has no taste nor smell, and is not soluble in water nor in alcohol. It undergoes no change, though kept exposed to the action of the air; neither does it alter speedily, though kept covered with water. When expos. ed to heat, it contracts very suddenly, and moves like a bit of horn, exhaling at the same time the smell of burning fea thers. In a stronger heat it melts.- When exposed to destructive distillation, it yields water, carbonate of ammonia, a thick, heavy, fetid oil, traces of acetic acid, carbonic acid, and carburetted hy drogen gas. The charcoal, as Hatchett ascertained, is more copious than that left by gelatine or albumen. It is very difficult to incinerate, owing to the pre sence of phosphate of soda, and some phosphate of lime, which form a glassy coat on the surface. A oonsiderable pro portion of carbonate of lime also remains after the incineration ofthe charcoal. Acids dissolve fibrin with considerable facility. Sulphulic acid gives it a deep brown colour.; charcoal is precipitated, and acetic acid formed. Muriatic acid dis solves it, and forms with it a green-colour ed jelly. The acetic, citric, oxalic, and tar taric acids also dissolve it by the assistance of heat ; andt he solutions, when concen trated, assume the appearance of jelly.
Alkalies precipitate the fibrin from acids in flakes, soluble in pot water, and re sembling getatine in its properties. From the recent experiments of Four. croy and Vauquelin on the muscular fi bres of animals, there can be little doubt that fibrin, when treated with hot nitric acid, undergoes a suit of changes. 1. It is converted into a yellow matter, which still possesses the fibrous texture Of fibrin, It has the property of converting vegeta ble blues to red, has a bitter taste, is but little soluble in water, and is insoluble in alcohol. It combines with alkalies, de composes their carbonates, unites to oils, and gives them rancidity and acid proper ties. To this substance, Fourcroy and Vat] queline have given the name of yellow acid. 2. By the farther action of the nitric acid, this yellow matter becomes more soluble, acquires a reddish tinge, and seems to become soluble in alcohol. 3. The last state into which it is brought by nitric acid seems to be that species of bit ter principle;which crystallizes and deto nates when combined with ammonia.
The alkalies, when diluted, have but little effect upon fibrin; but when concen-: trated 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 saturat ed with muriatic acid, a precipitate is ob tained 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 action 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 exam ined.