A moderate medicine which is of the same temperament as that to which it is applied, so as neither to dry, moisten, cool, nor heat, must not be called either dry, moist, cold, or hot; but whatever is drier, moister, hotter, or colder, is so called from its prevailing power. It will be sufficient for every useful purpose to make four ranks according to the prevailing temperament, calling that substance hot, according to the first rank, when it heats, indeed, but not manifestly, requiring reflection to demonstrate its existence: and in like manner with regard to cold, dry, and moist, when the prevailing temperament requires demonstration, and has no strong nor manifest virtue. Such things as are manifestly possessed of drying, moistening, heating or cooling properties, may be said to be of the second rank. Such things as have these properties to a strong, but not an extreme degree, may be said to be of the third rank. But such things as are naturally so hot as to form eschars and burn, are of the fourth. In like manner such things as are so cold as to occasion the death of a part are also of the fourth. But nothing is of so drying a nature as to be of the fourth rank, without burning, for that which dries in a great degree burns also; such are misy, chalcitis, and quicklime. But a substance may be of the third rank of desiccants without being caustic, such as all those things which are strongly astringent, of which kind are the unripe juice of grapes, sumach, and alum. * * * * * COMMENTARY. The following is a list of the ancient authorities on the Materia Medica and Pharmacy: Hippocrates (pluries); Dioscorides (de Materia Medica); Celsus (v); Scribonius Largus (pluries); Marcellus Empiricus; Pliny (H. N. pluries); Rei Rusticæ Scriptores; Apuleius (de Herbis); Antonius Musa (de Herba Betonica); Macer Floridus; Galenus (de Simpl.; de Comp. Med. sec. loc.; de Comp. Med. sec. gen.); Aëtius (i and ii); Oribasius (Med. Collect. xi et seq.); Sextus Platonicus (de Med. ex animal.); Zosimus Panopolita (de Zythorum confectione); Actuarius (Meth. Med.); Myrepsus (pluries); Psellus (de Lapidibus); Rhases (Contin. liber ult.; ad Mansor. iii); Avicenna (ii, et alibi); Serapion (de Simpl.; de Antidot.); Mesue (de Simpl.); Haly Abbas (Pract. ii and x); Averrhoes (Collig. v); Albengnefit (Libellus de Simpl. med. virt.); Geber (Chemia); Servitor (de Præpar. Med. i. e. xxviii Albucasis); Baitharis Præfatio ap. Casiri Biblioth. Arab. Hisp. p. 276; Ebn Baithar (Uebersetz von Sontheimer); Rei Rusticæ Scriptores Arabici ap. Casiri B. A. H.; Alchindus (Libellus de Med. compos. grad.)