The Mystical School found its most distinguished representative in Paracelsus; it derived its doctrine of the Macrocosm and the Microcosm from the Neoplatonists, and was largely imbued with alchemy and magic, the doctrines of the Cabala and the fanciful interpretations of the Bible. Later Paracelsists, Rosicrucians, and other speculators of the same character, such as Sir Kenelm Digby, brought the Mystical School of Medicine down to the seventeenth century. Our modern Theosophists are striving to restore much of the mystical teaching of Paracelsus and his followers. Again we meet the “astral bodies,” “the elementary spirits,” the cabalistic interpretations of the Bible, and the astrological absurdities of a pre-scientific period.
The Iatro-Chemical School really arose from Paracelsus, who amongst many absurdities held much important truth. Sprengel indicates Libavius of Saxony as the person who first cultivated chemistry apart from theosophy, and he names Angelus Sala as his successor. Lemery, in the middle of the seventeenth century, began to reform pharmaceutical chemistry. After Paracelsus chemistry became an indispensable study to every physician. Our word tartar, the scale which forms on the teeth, is of Paracelsian origin. He taught that the basis of all diseases was a thickening of the juices and the formation of earthy matter, which he called Tartarus, because it burns like the fire of hell. After Paracelsus we have Van Helmont, a true chemical discoverer who sought in chemistry a theory of disease of which his doctrine of fermentation in the body holds an important place. Next we have Sylvius, with his doctrine of the opposition of acid and alkali. Digestion he considered a process of fermentation or effervescence of the acid of the saliva and pancreatic juice with the alkali of the gall. When either the acid or the alkali predominated, disease was supposed to follow. The human body was regarded as a laboratory, the stomach as a sort of test tube. Boyle made objections to the doctrines of this school, and Herman Conring taught that the proper place of chemistry was not in physiology and pathology, but in pharmacy.
Viridet of Geneva endeavoured to prove that the fluids of the body are either acid or alkaline by experiment. Raimond Vieussens declared that he had discovered an acid in the blood and a ferment in the stomach. Hecquet opposed him, and said that digestion was not a process of fermentation, but of trituration. Pitcairn in England, Bohn and Hoffman in Germany, and Boerhaave in Holland opposed the iatro-chemists, and proved by observation that digestion is not fermentation, and that the acid and alkali theories of disease supported by Sylvius were false. By the influence and authority of these eminent physicians, the reign of the chemical school of physiology was overturned. The great fault of the iatro-chemists was their neglect of the effect of the solids of the animal body; they assimilated the work of the physician, as Whewell says, to that of the vintner or the brewer.
The Iatro-Mathematical or Mechanical School attacked, defeated, and superseded the iatro-chemists. According to this sect, the human body is a mere machine. Whewell explains that the Mechanical Physiologists came into existence in consequence of the splendid results obtained by the schools of Galileo and Newton. It was not so much the exposure of the weaknesses of the chemical physiology as the effects produced upon the world by the explanation of so many of the phenomena of the external universe by the men who had revolutionized astronomy by their discoveries; it was naturally hoped that that which served to explain the great world of matter might also elucidate the little world of man. Whewell divides the school into two parts—the Italian and the Cartesio-Newtonian sect. The Italian calculated and analysed the properties of the animal body which are undoubtedly purely mechanical, the Cartesio-Newtonians went much further than this and introduced many baseless hypotheses. The Italians occupied themselves with such calculations as the force of muscles and the hydraulics of the animal fluid. Borelli was the first great investigator on these lines; his work De Motu Animalium (Rome, 1680), treats of the forces and action of the bones and muscles. John and Daniel Bernouelli and Henry Pemberton pursued the same line of research. The principles of hydrostatics were brought to bear on the questions of the blood pressure and the breath. Keill endeavoured to estimate the velocity of the blood. The other school occupied itself with the corpuscular hypothesis in physiology. The organs were considered as a species of sieves. Both Newton and Descartes sought to explain physiology on a theory of round particles passing through cylindrical tubes, pyramidal ones through pores of a triangular shape, cubical through square openings. The diameter and curves of the different vessels formed subjects of calculations, and Bellini, Donzellini, and Guglielmini in Italy, Perrault and Dodart in France, Cole, Keill, and Jurin in England, devoted themselves to their study.[991]
The investigation of the size and shape of the particles of the fluids, and the diameter and form of the invisible vessels, formed a large part of the physiology of the beginning of the eighteenth century. Cheyne thought that fevers of the acute sort arise from glandular obstruction; and Mead, the royal physician and friend of Newton, explained the action of poisons on mechanical principles. The error of this school, as Whewell explains, lay in considering the animal frame as a lifeless compound of canals, cords and levers; the physicians, to its adherents, were merely hydraulic engineers. Some iatro-mathematicians were, in fact, at the same time teachers both of engineering and medicine.[992]
The Vital-Fluid School. The mechanical explanation of the motions of the animal body may satisfy some observers up to a certain point; there, however, they must confess their theory fails them. How does motion originate in the living frame? Friedrich Hoffman, of Halle (b. 1660), assumed a principle, material, yet of a higher kind than the adherents of the mechanical sect were inclined to recognise. This principle is exceedingly subtle, and is endued with great energy. It is the ether diffused through all nature, and which has its seat in the brain of animals and acts upon the body through the nerves. This vital fluid operates by laws which at one time were explained on the principles of a higher mechanics, of which we know little, and at another on metaphysical grounds, of which we know less. Naturally the discoveries connected with electricity imported a new element into these speculations. The vital principle was then held to be a modification of the electric fluid. John Hunter discerned it in the blood. Cuvier believed the vital fluid to be nervous. The objections to the doctrine of a vital fluid “as one uniform material agent pervading the organic frame,” are many. If the vital principle be the same in every part of the body, how does it happen that the secretions are all so different? How does the blood under the same influence furnish all the different fluids produced by the glands? How is it the liver secretes bile, the kidneys their peculiar fluid, the lachrymal gland the tears? The hypothesis of a vital fluid really explains nothing.
The Psychical School held the doctrine of an immaterial vital principle. This is at least as old as Aristotle,[993] who attributes the cause of motion to the soul. According to that philosopher the soul has different parts: the nutritive or vegetative, the sensitive, and the rational. Stahl, the great discoverer in chemistry, opposed the physiological theories of Hoffman, and declared that there is something in living bodies which cannot be accounted for by mechanics or chemistry. “All motion,” according to him, “is a spiritual act.” Nutrition and secretion belong to the operations of the soul; but he overlooked the fact that these are not peculiar to animals, but are characteristics of vegetables, which have no soul. Cheyne and Mead, Paterfield and Whytt in England inclined to Stahl’s views. Boissier de Sauvages defended them in France. Hoffman and afterwards Haller opposed them, the latter inventing the theory of Irritability.
Boerhaave (1668-1738), professor of medicine at Leyden, was a man of varied and profound erudition, conversant with the teaching of the ancient philosophers and the Greek and Arabian physicians; he was in addition fully conversant with all the discoveries connected with the healing art down to his own time. Beyond this he was a natural philosopher, chemist, botanist, and anatomist, and an indefatigable experimentalist. In teaching medicine he simplified its study as much as possible by rejecting the absurd and useless speculations which encumbered it, and putting in their place the facts which he believed his own experience and observation had enabled him to ascertain. He published his system of medicine in two volumes, one entitled the Instructions or Theory and the other the Aphorisms or Practice of Medicine. “These short treatises,” says Dr. Thomson,[994] “which gave to medicine a more systematic form than it had previously exhibited, are remarkable for brevity, perspicuity, and elegance of style, for great condensation of ideas, and for the number of important facts which they contain relative to the healthy and diseased states of the human economy.” The genius of Boerhaave raised the medical school of Leyden to the highest distinction. Princes in all countries sent him pupils; Peter the Great took lessons in medicine from him, and so great was his reputation that when a Chinese mandarin directed a letter to him, “To the illustrious Boerhaave, physician in Europe,” it was duly delivered. He held the study of Mind to form an important part of physiology. He taught that the change produced upon the extremity of the sentient nerve must be transmitted by the nerve to the brain before sensation can be produced. He considered the nerves to be hollow undulatory canals. He also held that each of the senses has its distinct seat in the common sensory or brain. His lectures on the mental faculties are full of varied and curious information. Considering the human body as a combination of various machines arranged in one harmonious whole, he endeavoured to explain its phenomena in health and disease on the principles of natural philosophy and chemistry to the almost entire exclusion of vital forces, which, however, he did not reject. He denied that all medical phenomena are to be explained upon mechanical principles. He lamented that “physiological subjects are usually handled either by mathematicians unskilful in anatomy, or by anatomists who are not versed in mathematics.” Yet his system of physiology embraced but a poor conception of the mystery of life. He says, “Let anatomy faithfully describe the parts and structure of the body; let the mechanician apply his particular science to the solids; let hydrostatics explain the laws of fluids in general, and hydraulics their actions, as they move through given canals; and lastly, let the chemist add to all these whatever his art, when fairly and carefully applied, has been able to discover; and then, if I am not mistaken, we shall have a complete account of medical physiology.”
It is to Boerhaave that we owe the peculiar chemical idea of affinity, that mutual virtue by which one chemical substance loves, unites with, and holds the other (amat, unit, retinet). He called it love. “We are here to imagine, not mechanical action, not violent impulse, not antipathy, but love, at least if love be the desire of uniting.” It is to Boerhaave, therefore, we are indebted for a view of chemical affinity which enables us to comprehend all chemical changes.[995]
The idea of affinity as marriage naturally leads to analysis as divorce. Thus affinity, imperfectly understood before the time of Boerhaave, made analysis possible. One of the first to express this conviction was Dr. Mayow, who published his Medico-Physical Tracts in 1674. He shows how an acid and an alkali lose their properties by combination, a new substance being formed not at all resembling either of the ingredients. He explains that, “although these salts thus mixed appear to be destroyed, it is still possible for them to be separated from each other, with their power still entire.”[996]