The school of the Asclepiadæ has been responsible for certain theories which have been more or less prominent during the earlier historical days. One of these which prevailed throughout the Hippocratic works is that of _Coction and Crisis_. By the former term is meant thickening or elaboration of the humors in the body, which was supposed to be necessary for their elimination in some tangible form. Disease was regarded as an association of phenomena resulting from efforts made by the conservative principles of life to effect a coction,--i.e., a combination of the morbific matter in the economy, it being held that the latter could not be properly expelled until thus united and prepared{025} so as to form excrementitious material. This elaboration was supposed to be brought about by the vital principles, which some called nature (_Physis_), some spirit (_Psyche_), some breath (_Pneuma_), and some heat (_Thermon_). The gradual climax of morbid phenomena has, since the days of Hippocrates, been commonly known as _Crisis_; it was regarded as the announcement of the completion of the union by coction. The day on which it was accomplished was termed _critical_, as were also the signs which preceded or accompanied it, and for the crisis the physician anxiously watched. Coction having been effected and crisis occurring, it only remained to evacuate the morbific material--which nature sometimes spontaneously accomplished by the critical sweat, urination, or stools, or sometimes the physician had to come to her relief by the administration of diuretics, purgatives, etc. The term "critical period" was given to the number of days necessary for coction, which in its perfection was supposed to be four, the so-called quarternary, while the septenary was also held in high consideration. Combination of figures after the Pythagorean fashion produced many complicated periods, however, and so periods of 34, 40, and 60 days were common. This doctrine of crisis in disease left an impress upon the medical mind not yet fully eliminated. Celsus was the most illustrious of its adherents, but it can be recognized plainly in the teachings of Galen, Sydenham, Stahl, Van Swieten, and many others. In explanation, it must be said that there have always existed diseases of nearly constant periods, these being nearly all of the infectious form, and that the whole "critical" doctrine is founded upon the recognition of this natural phenomenon. The Hippocratic books are full, also, of the four elements,--earth, water, air, and fire; four elementary qualities,--namely, heat, cold, dryness, and moisture; and the four cardinal humors,--blood, bile, atrabile, and phlegm.