2. For the latter, separating the qualities of ages, districts, and diseases, examined the practice of the art in a rational way. The _Empirici_, then, follow experience alone; the _Logici_ add reason to experience; the _Methodici_ observe neither the elements, nor seasons, nor ages, nor causes, but the substances of diseases alone. Chapter 5. On the four humors of the body. 1. Health is the integrity of the body and the compound (_temperantia_) made by nature from hot and moist which is the blood, whence also it has been named _sanitas_, as it were _sanguinis status_ (state of the blood). 2. Under the general name of _morbus_ (disease) all disorders of the body are embraced, to which the ancients gave the name of _morbus_ in order to indicate by the very name the power of death (_mortis_) which arises from it. Between health and disease the mean is cure, and unless it harmonizes with the disease it does not lead to health. 3. All diseases arise from the four humors, that is, from blood, bile, black bile, and phlegm. Just as there are four elements so also there are four humors, and each humor imitates its element: blood, air; bile, fire; black bile, earth; phlegm, water. There are four humors, as four elements, which preserve our bodies. 4. _Sanguis_[284] (blood) took its name from a Greek source, because it invigorates, sustains and gives life to the body. _Cholera_[285] (bile) the Greeks named because it is ended in the space of one day, whence it was named _cholera_, that is, _fellicula_, that is, effusion of bile (_fel_). For the Greeks call bile χολή. [284] The derivation which Isidore had in mind was probably ζῆν (to live). [285] The sentence is a confused one. Isidore probably had in mind the derivation of _cholera_ from χολή and ῥέω. 5. _Melancholia_ (black bile) is named because an abundance of bile has been mixed with the dregs of black blood.... 6. _Sanguis_ in the Latin is so-called because it is _suavis_, whence men in whom _sanguis_ is predominant are pleasant and bland. 7. _Phlegma_ they have named because it is cold. For the Greeks call cold φλέγμονα. According to these four humors the well are governed, and from them the diseases of the infirm arise. For when they have grown too great beyond the course of nature, they cause illnesses. 8. From blood and bile acute disorders come, which the Greeks call ὀξέα; from phlegm and black bile troubles of long standing, which the Greeks call χρόνια. Chapter 6. On acute diseases. 1. _Oxea_ is acute disease which either quickly passes or more quickly kills, as pleurisy, phrensy, for ὀξὺ in Greek means swift and sharp. χρόνια is prolonged bodily disease which lingers through many seasons, as gout, phthisis.... Certain disorders have received their names from causes proper to them. 2. _Febris_ (fever) is derived from _fervor_, for it is an excess of heat.