The physicians of the two preceding periods have not emitted any general law in Therapeutics ; they regulated their practice instinctively upon the following plan : when a remedy has cured any disease, it should cure all other identical diseases. This axiom, incontestably true in itself, is but a fragment of one much more general, which embraces the whole philosophy of causes, and may be

expressed thus: the same agents, placed in the same identical circumstances, will always produce the same effects. But a proposition so universal, which appertains to medicine no more than to the other sciences, and which takes no account of the internal action of medicines, appeared too superficial to philosophical physicians, and too vague to practitioners who desired a rule less common ; in short, one more directly related to the healing art. Consequently, both parties sought another fundamental principle, and the following is the result of their speculations on this subject: it was held that there always exists a species of antagonism between the cause of the morbid phenomena and the active properties of the remedies that cured them ; or rather, between the pathological modification of the organism and the curative impulse given to the economy by the treatment. This law was expressed by the following aphorism : contraria contrariis curantur.

The greater number of medical writers adopted this principle, and endeavored to establish the practice of medicine upon it. Now, two things were necessary for that : first, to discover the essential cause of each disease, or the primitive lesion that constitutes each morbid species ; secondly, to determine the mode of action and the degree of energy of therapeutic agents, so that the practitioner may choose from among them, those which were more directly contrary to the affection he is called upon to combat. The course of this history will show us the results of the efforts made at different epochs to attain this double end, and we shall have occasion more than once to discuss the validity of hypcenantiosis, or the doctrine of contraries. At present it will suffice to say, that from its commencement this principle has not been universally adopted. Thus, the author of the book entitled "Ancient Medicine," one of the most philosophic of the collection, devotes several paragraphs to the refutation of this axiom. And we read in the treatise on the Regions of Man, that diseases are sometimes cured by contraries, sometimes by similars, and, finally, sometimes by remedies which have neither similitude nor opposition.(See § 67, 68, 69, 70, Gardeil)

We shall conclude this chapter by giving examples of the manner in which the practitioners of those times applied the general principles of Therapeutics to the treatment of particular diseases. The following cases appear to me to be the best arranged and most complete of any of those recorded in the collection :

TREATMENT OF PLEURISY AND PERIPNEUMONIA.

"It is necessary to examine in the following manner the peripneumonic and pleuritic affections : if the fever is acute ; if there is pain in one or both sides of the chest ; if the patient suffers during expiration ; if he coughs, and the expectoration is rusty or livid, or thin and frothy, or of a blood-red - if, in fine, it differed at all from that which is natural, . the following course must be pursued : the pain extending above and towards the clavicle, or towards the vein and the arm, the internal vein of the arm on that side should be opened. The quantity of blood drawn should be proportional to the constitution of the body, the season of the year, the age and color of the patient ; and if the pain is acute, the bleeding should be boldly pushed to syncope ; afterward an injection is to be administered.

" If the pain occupies the inferior region of the chest, and if the tension is great, you should prescribe for pleuritics a mild purgation ; but they must taste nothing else while the medicine is operating. After the purgation they should have an oxymel. The purgation should not be administered till the fourth day : during the first three days injections should be employed ; but if they are not sufficient, the purge should be given, as above said. He must be watched until the fever ceases and the seventh day is attained ; after that, if he appears out of danger, he may take a little barley-water, weak at first, and sweetened with honey. If the convalescence progresses and the respiration is good, the tisane may be given twice a day, and be gradually increased in quantity and strength ; but if the convalescence is slow, the drink must be lessened, and for nourishment a small quantity of a weak tisane once a day. It should be given when the patient is in the best condition, which may be known by the appearance of the urine.

" To those who approach the close of the disease, it is not necessary to give the tisane, before you see the coction manifested in the urine or expectoration; nevertheless, if, when purged, the patient has abundant evacuations, it is necessary to give the tisane, but in less quantity and weaker, otherwise the emptiness of the vessels would allow him neither to sleep, nor to digest or await the crisis. With this exception, the crude humors should be liquefied, and whatever has been the obstacle, be ejected: then nothing prevents alimentation. The expectoration is perfectly concocted when it appears like pus : the urine, also, when it has a red sediment, like brickdust.

"As to the pains in the side, nothing contra-indicates the use of fomentations and wax plasters. The legs and loins should be rubbed with warm oil and then anointed with fat. The hypochondria should be covered as high as the breasts with a flaxseed poultice. When the peripneumonia has reached its height, nothing can be accomplished without purgation : it is bad if the patient has dyspnea, or the urine be thin and acrid, or there be sweats around the neck and head. These sweats indicate danger in proportion to the violence of the disease, which is known by the suffocation and rattling, which increases and produces death, unless there supervene an abundant flow of viscid urine or of concocted sputa. Whichever of these two phenomena supervenes, it indicates resolution."

An eclegma is prescribed for peripneumonia, with galbanum and grains of pine-seed, in Attic honey. Other expectorants are employed, such as worm-wood (Artemisia abrotanum, Lin.) , and pepper in oxymel ; purgatives: boil black hellebore (Helleborus orientalis, Lin.), and give it as a drink to pleuritics, at the commencement, and while the pain is felt. A useful remedy in affections of the liver, and in pains proceeding from the diaphragm, is a drink of opoponax (Pastinacae opoponax, Lin.), boiled in oxymel and strained. In general, a remedy, which is to act on the stools or urine, should be given in wine, and in honey ; if to act on the stools alone, it should be given in a much larger quantity of diluted oxymel. 

From History of Medicine by P.V. Renouard M.D.