that their delicacy and perfection immeasurably exceed any with which sense has made us acquainted. 245. iii. The vitality of the blood is proved by the process of organization. We can trace only a few steps of this process, but these are sufficient to establish the point in question. Blood effused from living vessels into the substance, or upon the surface of living organs, solidifies without losing vitality. If a clot of blood be examined some time after it has thus become solid, it is found to abound with blood-vessels. Some of these vessels are obviously derived from the surrounding living parts. The minute vessels of these parts, as can be distinctly traced, elongate and shoot into the clot. The clot thus acquires blood-vessels of its own. By degrees a complete circulation is established within it. The blood-vessels of the clot act upon the blood they receive just as the vessels of any other part act upon their blood, that is transform it into the animal matter it is their office to elaborate. In this manner a clot of blood is converted into a component part of the body, and acquires the power of exercising its own peculiar and appropriate functions in the economy. 246. But while, in this process, some of the vessels of the clot can be distinctly traced from the surrounding living parts, others appear to have no communication with those parts, at all events no such communication can be traced. These vessels, the origin of which cannot be found external to the clot, are supposed by some physiologists to be formed within it. Within the living egg, during incubation, certain motions or actions are observed spontaneously to arise, which terminate in the development of the chick. Analogous motions arising within the clot terminate, it is conceived, in the development of blood-vessels. According to this view, a simultaneous action takes place in the clot, and in the living part with which it is in contact; each shooting out vessels which elongate, approximate, unite, and thus establish a direct vital communication. Whether this view of the process of organization be the correct one or not does not affect the present argument. It is certain that a clot of blood surrounded by living parts becomes organized; it is certain that no dead substance surrounded by living parts becomes organized; it follows that the blood possesses life. 247. Health and life depend on the quantity, quality, and distribution of the blood. The chief source from which the blood itself is derived is the chyle: hence too much or too little food, or too great or too little activity of the organs that digest it, may render the quantity of the blood preternaturally abundant or deficient; or though there be neither excess nor deficiency in the quantity of nourishment formed, parts of the blood which ought to be removed may be retained, or parts which ought to be retained may be removed, and hence the actual quantity in the system may be superabundant or insufficient.