Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 1, 1802).djvu/321

Rh yielding in distillation a volatile spirit, a great quantity of phlegm, and fetid oil; lastly, there remains a charred matter, which, when burnt in the open air, leaves a white earth similar to calcined hartshorn. According to some chemists, however, it contains both an acid and an alkali. But the most remarkable circumstance in the blood, is its texture, which consists of millions of red globular particles, or more properly, as Mr. calls them, flat vesicles, each of which has a little solid sphere in its centre. He observes, that they are flat in all animals, of very different sizes in different creatures, and impart to the blood its red colour. In man, they are small, perfectly flat, and appear to have a dark spot in the middle. To see them distinctly, he diluted the blood with fresh serum. Their shape he supposed to be of great importance, but it can be altered with a mixture of different fluids. By a determinate quantity of neutral salt contained in the serum, this fluid is adapted to preserve those vesicles in their flat shape; for, if mixed with water, they become round, and dissolve perfectly, but on adding a little of any neutral salt to the water, they remain in it without dissolving, or any alteration of their form.

The uses of the blood in the animal economy are so various and important, that some have not scrupled to maintain that it is possessed of a vital principle, from which the life of the whole body is derived. This opinion was formerly entertained by, and has lately been revived and supported, with many ingenious, though inconclusive, arguments, by. Yet so much is certain, that the blood stimulates the cavities of the heart and vessels to contract, that its circulation contributes to generate the heat of the body, and propagate it to the remotest parts; in short, that it nourishes every part, and supplies all the secretions, which, without exception, are separated from the blood. Hence it forms the bones, ligaments, tendons, membranes, muscles, nerves, vessels, and the whole organized body.

The blood is of different degrees of viscidity in different animals, and even in the same creature, at different times. It always possesses a considerable degree of tenacity; which, however, is remarkably greater in strong than in weak animals: thus, the blood of bulls was used by the ancients as a poison, on account of its extreme viscidity, which renders it totally indigestible by the human stomach.

Animal blood was formerly held jn great esteem, as a medicine in various diseases; for instance, the blood of goats and some other creatures was employed by the followers of, and recommended even by the late Dr. in pleuritic attacks. But at present the principal use of blood is confined to the arts, for making Prussian blue; sometimes for clarifying certain liquors; and very large quantities are used in the manufacture of loaf sugar. In horticulture, it is recommended as an excellent manure, when poured in spring on the roots of fruit-trees, having previously removed the soil round the trunk: thus employed, it promotes the growth of the tree, and enriches its fruit. A mixture of blood with quick-lime, forms an exceedingly strong cement, and has therefore been used in preparing chemical lutes, as well as in making the