The same plan was adopted by Ilerrigonius, Steno, and others ; and, at last, with peculiar success by Bo relli, in his valuable work De motu 4nimalium. Till his time it had been generally believed, that, in muscular action, nature produced a great force by a small effort ; and that she thus effected her purpose by certain levers, or mechanical powers, supposed to exist in the muscles or tendons. Borclli sheaved clearly that no such powers exist in either, and that bones are the only levers in the body. He proved, likewise, that these levers were of a kind very different from what had been imagined ; and, from the direction of the muscles, from the obliquity of their insertion, from the place of their insertion near the joint, from its situation between the fulcrum, and the re sistance, lie demonstrated, that nature, instead of produ cing great force by a small effort, was on many occa sions obliged to exert a power by many hundred times greater than the weight which it had to overcome.
Having thus ascertained the nature of those levers, he proceeded next to calculate the strength of the dif ferent muscles, and found, that many which, in the dead body, scarcely support the weight of the bones to which they are attached, do in the living exert a force equal to some thousands of pounds. All these conclu sions he drew from data universally admitted ; but he had an opinion with regard to the structure of the mus cular fibre, which would make their force almost in credible. On this hypothesis, the force of only three muscles of the hip-joint is equal to 3-75420 pounds. His observations on the forms and movements of dif ferent animals, of men, quadrupeds, birds, fishes, and insects, are not only highly interesting to the naturalist, but might be studied with advantage by the surgeon who wishes to improve the mode of cure in luxation and fracture, and in all those cases where muscular action is materially concerned. Borelli was probably the first who clearly demonstrated the immense force of a mus cular stomach, and has given a detail of many experi ments, which, when afterwards repeated by the Abbe Spalanzani, were greatly admired, because they were ignorantly supposed to be new.
His success in explaining muscular motion, induced him to apply mathematical reasoning to the other func tions both in a state of health and disease ; and his friend Bellini, carrying it still farther, was reckoned the in ventor of what has been called mathematical medicine : a discovery deemed so important, that it has been styled " nobilissimum atgue utilissimum invention ;" and was thought by some little inferior to the discovery of the circulation by Harvey. This discovery, if such it may
he called, found a warm and strenuous advocate in his friend Pitcairn, who afterwards published the Physic°. mechanical Elements of Medicine. The celebrated Boerhaavc, Pitcairn's pupil, and the most illustrious character of his time, by giving his sanction likewise to many of its principles, seemed to establish it in the schools of physic.
The animal system was now considered merely as a mechanico-hydraulical machine, and many strange the ories were formed concerning the lentos, and fluidity of the humours ; the shape, magnitude, and gravity, of the particles ; and the cavities of the vessels, supposed capable of receiving only those of a certain kind, which, if they chanced to wander from their place, occasioned disease by an error loci. Carried away by enthusiasm, the mechanical physicians could not pen (Ave that mot; of their conclusion:: were drawn from hypotheses, sup ported neither by observation nor expe:iment ; and I'M eager were they in their favor: te pursuit, that the) seemed to be offended when any other mode of reason ing was suggested. " Since the human body," said Di Friend, " is nothing but a fine contextme of and fluids, which observe the rules of nit hanisin, it is amaz ing to find that men should think of an) Other principh than the mechanical to explain it by. ‘Vould any ow:," he adds, " go so much out of the a ay, as to account for the motions of a watch from the precarious doctrine acids and alkali ? or would he make use of the etherial matter of Des Cartes to solve all the appearances of hy drostatics ?" Such opinions of the importance of a favourite science might, indeed, be mtturid ; but they were carried to such extravagance, and led to consequences so very absurd, that mathematical reasoning has, for some thin past, been almost entirely excluded from physiology. It is but fair, however, to confess, that its enemies have been as imprudent in rejecting it altogether, as Benin. and Pitcairn in extending it too far. No other species of reasoning could ever have explained the motions of animals ; shewn the force which the heart and stomach exert in their contractions ; the velocity of the blood : its momentum and quantity in different vessels ; and the effect of the several angles at which the branches rise front their trunks. It may be added, that no other mode of reasoning has been so successful in giving a rational theory of vision ; in explaining the organs and pheno mena of sound ; and in explaining the relative propor tions of the different excretions, and the causes which affect them.