Page:Popular Science Monthly Volume 2.djvu/705

Rh after decision by the Parliament, Du Châtelet, the deputy prosecutor, publishes an edict proscribing it in the name of the law. What was the real cause of the downfall of the system? That it rested on mistaken physiological ideas. The blood was still regarded as the sole principle of instinct, intellect, and life. The physician who practised transfusion could only defend it by hypotheses, and justify its employment by explanations and reasonings. The labors of our own time alone can give it lasting life; transfusion will revive two hundred years later to a new and vigorous existence, for it will rest on the best-established truths of physiology.

The light thrown by Harvey upon the knowledge of life did not give a complete account of the mechanism of our organization; the opening of an era of progress by grand discoveries awaited the coming of Lavoisier, at the close of the last century. General physiology was founded at that period, and the office and functions of the blood were soon learned by degrees and clearly settled. Between 1815 and 1830 the history of transfusion passes into a new phase. Atwood, Blundell, and Diffenbach, make it generally known by important works. In France two eminent savants, Prevost and Dumas, devote themselves to new researches, of which the "Annals of Chemistry," for 1821, preserve the record; but the transfusion of blood has made decisive steps only within the last twenty years, due particularly to the labors of a modern physiologist, Brown-Séquard. We shall sketch the bold and interesting experiments he employed in attacking and dealing so successfully with the most difficult problems of life; the history of physiology hardly presents a more exciting and instructive page. For its full comprehension, the nature and functions of the blood must first be explained.

As it circulates within the vessels, the blood is to be regarded as a fluid in which an innumerable quantity of colored corpuscles are floating. On account of their shape, these little bodies are called globules, and they are invisible without the aid of magnifiers; in fact, their diameter scarcely exceeds two ten-thousandths of an inch. The vehicle of these globules has the scientific name of plasma; the matters elaborated by the digestive apparatus, and the products of decomposition of the tissues, are the essential components of this liquid; albuminoid substances, analogous to white of egg, fats, sugars, salts of a mineral nature, appear in it under different forms, and constantly repair it; while the excretory ducts as constantly carry off from it those particles that become useless to life. The elements of our tissues have their nutrition kept up by a constant movement of supply and withdrawal, new molecules replace the old ones, and acts of assimilation and disassimilation find by turns in the plasma their point of origin and completion. The blood-globule is nourished just as the constituent parts of the glands, the muscles, the nerves, and the brain