When we have taken from the muscles their colouring substance by repeated washings, there remains a white fibrous texture, from which we can still extract albumen by ebullition, which rises in scum, gelatine by suffering it to grow cold, extractive matter which has a deep colour, by letting it settle, and some phosphoric salts. When all these substances have disappeared, the residue of the muscle is a fibrous substance, of a greyish colour, insoluble in warm water, soluble in the weak acids, giving out much azote from the action of the nitric acid, and presenting all the characters of the fibrin of the blood. It appears, as Fourcroy has remarked, that this substance is truly the nutritive substance of the muscle, that which, continually exhaled and absorbed, contributes to its nutritive phenomena more than all the others; it constitutes the essence of the muscle, it especially characterizes it, as the phosphate of lime is the nutritive characteristic matter of the bones. Is this substance formed in the blood and carried from it to the muscle, or is it formed in the muscle by nutrition, and thence carried to the blood? I know not. Whichever may be the case, it appears to experience very great varieties in its exhalation and absorption. The state of laxity, of cohesion, the thousand various appearances of the muscular texture, appear to belong in part to these varieties of proportion. Thus the phosphate of lime or gelatine, diminished by nutrition, give to the bones softness or brittleness. It is in this fibrous and essential portion of the muscle, that particularly resides the faculty of crisping by the action of caloric, whether by plunging a muscle into boiling water, or exposing it to the fire; for this crisping is as evident in the muscle deprived of its colouring matter, its gelatine, its albumen, and even a portion of its extractive substance as in the ordinary muscle. There is in general a constant relation between the quantity of this fibrous substance contained in the muscles, and the quantity that the blood contains of it. In the strong, vigorous, sanguineous temperaments, as they are called, the muscles are thick and much more fibrous. In all the slow cachexiæ in which the blood is impoverished, the pulse small and feeble and in which muscular nutrition has had time to share but little of the fibrin of the blood, the muscles are small, weak, soft, &c. In general, the muscles and the blood are always in constant relation, whilst other systems often predominate and whilst this fluid seems to be in less quantity in the economy.