Nitrogen 1 14 19.72 Carbon 6 36 50.70 Ilydrogen 5 5 7.04 Oxygen 2 16 22.54 1 71 100.00In reference to this atomic estimate, which is suggested by Leopold Gmelin,* Berzelius observes, that from the feeble saturating power of fibrine, its equivalent number is probably very high, that is, that it includes a larger number of simple atoms; but as we have at present no accurate means of determining its combining proportion or saturating power, its atomic constitution cannot be satisfactorily determined. Moreover, it appears that in the above analyses the fat was not separated, nor is any notice taken of the minute portion of sul phur, the presence of which has been above adverted to.
When Berzelius first obtained fat from fibrine by digesting it in alcohol and in ether, he con cluded that it arose from the decomposition of a portion of the fibrine by those agents ; that it was a product and not an educt ; but the sub sequent experiments of Chevreul leave no doubt that the fat exists ready formed in the blood. This fat is very soluble in alcohol, and the solution is slightly acid; when it is burned, the ash, instead of being acid, like that of the fatty matter of the brain, is alkaline, whence it appears that it existed saponified, or partly so, in the blood.
Another important variety of fibrine is that which 'constitutes muscular fibre, but it is so interwoven with the nerves and vessels and cellular and adipose membrane, that its pro perties are probably always more or less modi• fled by foreign matters. The colour of muscles appears to depend upon that of the blood in their capillary vessels; and their moisture is referable to water, which may be expelled by drying them upon a water-bath, when they lose upon an average 75 per cent. If muscular fibre in thin slices is washed with water till all soluble matters are removed, the residue, when carefully dried, does not exceed 17 or 18 per cent. of the original weight.
To obtain the fibrine of a muscle, it must be finely minced and washed in repeated portions of water at 60° or till all colouring and soluble substauces are withdrawn, and till the residue is colourless, insipid, and inodorous; it is then strongly pressed between folds of linen, which renders it semitransparent and pulverulent. Berzelius observes that in this state it becomes so strongly electro-positive when triturated, that the particles repel each other and adhere to the mortar, and that it stil retains fat which is separable by alcohol or ether. When long boiled in water, it shrinks,
hardens, and yields a portion of gelatine de rived from the insterstitial cellular membrane ; the fibrine itself is also modified by the con tintfed action of boiling water, and loses its solubility in acetic acid, which, when digested with it in its previous state, forms a gelatinous mass soluble in water, but slightly turbid from the presence of fat and a portion of insoluble membrane, derived apparently from the vessels which pervaded the original muscle. It is soluble in diluted caustic potassa, and precipi tated by excess of muriatic acid, the precipitate being a compound of fibrine with excess of muriatic acid, and which, when washed with distilled water, becomes gelatinous and soluble, being reduced to the state of a neutral muriate of fi brine." When the fibrine of muscle is mixed with its weight of sulphuric acid, it swells and dis solves, and, when gently heated, a little fat rises to the surface and may be separated : if the mass is then diluted with twice its weight of water and boiled for nine hours, (occasion ally replacing the loss by evaporation,) am monia is formed, which combines with the acid, and on saturating it with carbonate of lime, filtering, and evaporating to dryness, a yellow residue remains, consisting of three distinct products: two of these are taken up by digestion in boiling alcohol of the specific gravity of .845, and are obtained upon evapo ration ; this residue, treated with alcohol of the specific gravity of .830, communicates to it (1) a portion of a peculiar extractive matter, and the insoluble remainder (2) is white, soluble iii water and crystallisable, and has been called by Braconnot lcucitte.1- It fuses at 2120, ex haling the odour of roasted meat, and partly sublimes : it is difficultly soluble in alcohol. It dissolves in nitric acid, and yields on eva poration a white crystalline compound, the nitro-leucic acid. The portion of the original residue which is insoluble in alcohol (3) is yellow, and its aqueous solution is precipi tated .by infusion of galls, subacetate of lead, nitrate of mercury, and persulphate of iron. It appears therefore that the products of the action of sulphuric acid upon the fibrine of muscle, are, 1, an extractive matter soluble in alcohol ; 2. leucine; and 3. extractive, inso luble in alcohol but soluble in water.
( 1 V. '1'. Braude.)