But or all the sciences, none has made bolder pre • tensions than chemistry to explain the functions of the animal system. The first who suggested the use of chemistry in physiology was Paracelsus: a man of sin• gularly eccentric manners, keen, rash, ignorant, conceit ed, and notorious for that insufferable arrogance by which the weak-minded in prosperity are generally characterised. Ambitious to an excess of popular ap plause, he would allow no merit to any other person ; and, for that reason, was particularly violent against all those of his own profession who had acquired any repu tation. Having excited the admiration of the t ulgar and credulous, by sonic remarkable cures which he per formed by means of mercury and opium, he fancied that he was something more than human ; and, uniting cunning with ambition, endeavoured to impose himself on the world, not only as the first physician, but the first philosopher and divine then existing. Thus idly flattering his own vanity, he, in contemptuous derision, styled I lippocrates, Galen, and Avicenna, /um:Qum/Ws, and burnt the works of the two latter publicly at Basil ; He threatened next to overturn the system of Aristotle, and to send back to school, the Pope, Luther, and Zuin glius, as he had already sent Hippocrates, Galen, and Avicenna.
The art of anatomy, of which he was totally ignorant, he affected to despise as local, material, and gross, and worthy of no attention. He proposes a new kind of anatomy, however, which was to consist in the chemical analysis of the different organs ;—" this," he exclaims, " is alone the true, this the genuine, this the noblest kind of anatomy !" By this anatomy he expected to find the kinds and propoitions of the three great chemical principles of that time, sulphur, mercury, and salt : the sulphur, what ascended in flame ; the mercury, what as cended in smoke ; and the salt, what remained alter um bustion.
As he believed that the animal fabric is a microcosm, or little world, governed by a spirit which he called Archoeus, so he also imagined, that, like the great world, it contains the principles of all animals, minerals, and vegetables ; and, by the power of fancy, or, rather, by the aid of the poet Manilius, who wrote on astronomy in the time of Augustus, he discovered its sun, its moon, and its planets ; and asserts, that it is necessary for a physician to know, likewise, its east and its west, its meridian line, its polar axis, the tail of the Dragon, and its sign Aries.
It was not to be expected that chemistry, recom mended by such a person, could receive much attention from physiologists. His writings, however, contributed to free them from the shackles of Galen, and rendered chemical studies so fashionable, that Borelli, in his Bibliotheca Chymica, published in 1653, enumerates no fewer than 4000 persons who had been engaged in that branch of science, though he mentions none but those of his own knowledge.
One would naturally imagine, that, from their joint labours, much light would be thrown on the animal economy. But Boerhaave, in his history of Chemistry,
complains, that many of those engaged in this study, by their low character, their dissipated lives, their preten sions to magic, and their mercenary views, not only re tarded the progress of the science, but prevented man kind from reaping the advantage of their discoveries. A circumstance so unfavourable to the chemists was not likely to be overlooked by their opponents the mathe maticians : Part of that odium so justly attached to the character of the men was transferred to the science, and thus chemistry was rejected from physiology.
Among those who contributed to restore it, we are chiefly indebted to the honourable Mr Boyle, Homberg, Mayow, Geoffrey, the younger Lemery, Stahl, and Hoff man. Boyle, the earliest of these writers, not only analysed a considerable number of animal substances, but pointed out several advantages which anatomists might derive from the study of this science. He was the inventor, likewise, of what has been called the pneumatic philosciphy, which was afterwards so much studied by Mayow and Hales, and has been so much im proved by our countryman Dr Black, whose merit as a chemist will perpetuate his memory to the latest ages. By this discovery, chemical analysis is brought to a high state of perfection ; and the modern chemistry has already ascertained, in a much more satisfactory man ner than had ever been done before, the component parts of many of the animal solids and fluids : having shewn farther, that, in many cases, the proportions vary according to age, health, and disease, it gives us hopes that it will be able to provide better remedies than are yet known, for many of the morbid changes which take place.
Besides ascertaining the particular nature of those changes, chemistry has furnished the best explanation of two very important functions—digestion and respira tion. The ancients, as has been already observed, generally imagined, that the food was prepared by putres cence or concoction, to which Erasistratus afterwards added a muscular force. But neither putrescence, con coction, nor grinding, nor even the hypotnesis of fer mentation, could ever explain how, in certain stomachs, the hardest bones are converted into chyle, until the chemists, from frequently observing the processes of their laboratories, began to suspect, that a certain liquor was secreted in the stomach, possessing the properties of a chemical solvent. Boyle and Ray ascertained its existence : Grew proved, that it could not act upon living bodies ; and others observed, that it varied ac cording to the nature of the food and the state of the stomach, that it was different in different animals, and even in the same animal at different periods. These facts have certainly helped to explain a great number of curious phenomena, with regard to digestion.