blood consists of a complex liquid, in which are suspended a multitude of minute cells, some red, others colorless. When the blood is removed and dies, it clots or partially solidifies, and is found to contain a network of extremely fine fiber, to which the name of fibrin is applied. A similar change takes place in the substance of the muscle after death. It stiffens, and this stiffening, or rigor mortis, is effected by the formation of a clot analogous to the coagulation of the blood, and the substance of this clot (myosin) is so nearly like the fibrin of the blood and the material of the muscular fiber (syntonin) that for our purpose they may be all described as varieties of fibrin.
The properties of fibrin, so far as cookery is concerned, place it between albumen and gelatine; it is coagulable like albumen, and soluble like gelatine, but in a minor degree. Like gelatine, it is tasteless, and non-nutritious alone. This has been proved by feeding animals on lean meat, which has been cut up and subjected to the action of cold water, which dissolves out the albumen and other juices of the flesh, and leaves only the muscular fiber and its envelopes. The same is the case with the spontaneously coagulated fibrin of the blood; it is, when washed, a yellowish, opaque, fibrous mass, without smell or taste, insoluble in cold water, alcohol, or ether, but imperfectly soluble if digested for a considerable time in hot water.
The following is the chemical composition of these three constituents of lean meat, according to Müller:
| Albumen. | Gelatine. | Fibrin. | |
| Carbon | 53·5 | 50·40 | 52·7 |
| Hydrogen | 7·0 | 6·64 | 6·9 |
| Nitrogen | 15·5 | 18·34 | 15·4 |
| Oxygen | 22·0 | 24·62 | 23·5 |
| Sulphur | 1·6 | . . . . | 1·2 |
| Phosphorus | 0·4 | . . . . | 0·3 |
| ———— | ———— | ———— | |
| 100.0 | 100.0 | 100.0 |
There are two other constituents of lean meat which are very different from either of these, viz., Kreatine and Kreatinine, otherwise spelled creatine and creatinine. These exist in the juice of the flesh, and are freely soluble in cold or hot water, from which solution they may be crystallized by evaporating the solvent, just as we may crystallize common salt, alum, etc. They thus have a resemblance to mineral substances, and still more so to some of the active constituents of plants, such as the alkaloids, theine, and caffeine, upon which depend the stimulating or "refreshing" properties of tea and coffee.
Their chemical composition and general relations have suggested the theory that they are the dead matter of muscle, the first and second products of the combustion which accompanies muscular work, urea being the final product. According to this, their relation to the muscle is exactly the opposite of that of the albuminous juice, this
