It would be leading to a detail which is incompatible with our present purpose to follow these speculations, or to give an account of the doctrines of the mechanical physicians, who believed that every operation of the animal economy was explained by comparing it to a system of ropes, levers, and pulleys, united with a number of rigid tubes of different lengths and diameters, containing fluids which, from variations in their impelling causes, moved with different degrees of velocity: or of the chemical physicians, whose manner of theorizing and investigating would have qualified them better for the occupation of the brewer or of the distiller than for that of the physician. All these speculations are idle fancies, without any evidence whatever to support them; and it has been argued that, for this very reason, they must have been without any practical result, and that, therefore, if they were productive of no benefit, they were, at least, innoxious. No opinion can be more false or pernicious. These wretched theories not only pre-occupied the mind, prevented it from observing the real phenomena of health and of disease, and the actual effect of the remedies which were employed, and thus put an effectual stop to the progress of the science: but they were productive of the most direct and serious evils. It is no less true in medicine than in philosophy and morals, that there is no such thing as innoxious error; that men’s opinions invariably influence their conduct; and that physicians, like other men, act as they think. Asclepiades, whose mind was full of corpuscles and interstices, was intent on finding suitable remedies, which he discovered in gestation, friction, and the use of wine. By various exercises he proposed to render the pores more open, and to make the juices and corpuscles, the retention of which causes disease, to pass more freely. Hence he used gestation from the very beginning of the most burning fevers. He laid it down as a maxim that one fever was to be cured by another; that the strength of the patient was to be exhausted by making him watch and endure thirst to such a degree that for the first two days of the disorder he would not allow them to cool their mouths with a drop of water. Abernethy’s regulated diet is luxurious living compared to his plan of abstinence. For the three first days he allowed his patients no aliment whatever; on the fourth, he so far relented as to give to some of them a small portion of food; but from others he absolutely withheld all nourishment till the seventh day. And this is the gentleman who laid it down as a maxim that all diseases are to be cured “_Tutò, celeriter et jucunde_.” To be sure he was a believer in the doctrine of compensation; and in the latter stage of their diseases endeavoured to recompence his patients for the privations he caused them to endure in the beginning of their illness. Celsus observes that though he treated