Some writers have supposed that certain of the uncleannesses alluded to in the Book of Leviticus have reference to this complaint; and it is quite possible that in old times it acquired a much more severe character than it ever has now, owing to neglect or improper treatment. Psora, in Greek, and the equivalent term Scabies, in Latin, are supposed to have at least included the itch, though in all probability those words comprehended a number of skin diseases which are now more exactly distinguished. Hippocrates mentions psora, and apparently treated it solely by the internal administration of diluents and purgatives. Aristotle mentions not only the disease but the insects found, he said, in the blisters. Celsus advocated the application of ointments composed of a miscellaneous lot of drugs, such as verdigris, myrrh, nitre, white lead, and sulphur. Galen hints at the danger of external applications which might drive the disease inwards. In Cicero, Horace, Juvenal, and other of the classical writers, the word scabies is used to indicate something unnatural; showing that it had come to be adopted metaphorically. The Arab writers are much more explicit. Rhazes, Haly Abbas, and Avicenna are very definite in their descriptions of the nature of the complaint, and how it is transmitted from one person to another; but Avicenna’s mode of treatment was directed to the expulsion of the supposed vicious humours from the body by bleeding and purgatives, especially by a purgative called Hamech. At the same time he advised that the constitution should be reinforced by suitable diet and astringent medicines. Avenzoar of Seville, a remarkable observer, who lived in the twelfth century, alludes to a malady of the skin, common among the people, and known as Soab. This, he says, is caused by a tiny insect, so small that it can scarcely be seen, which, hidden beneath the epidermis, escapes when a puncture has been made. One would have supposed that the doctors were at that time on the eve of understanding the itch correctly, and in fact the writers of the next few centuries were at least quite clear about the acarus. Ambrose Paré, for example, who lived through the greater part of the sixteenth century, uses this language:--“Les cirons sont petits animaux cachés dans le cuir, sous lequel ils se trainent, rampent, et rongent petit par petit, excitant une facheuse demangeaison et gratelle;” and elsewhere “Ces cirons doivent se tirer avec espingles ou aiguilles.” All this time, however, the complaint was regarded as a disturbance of the humours which had to be treated by suitable internal medicines. In a standard work, _De Morbis Cutaneis_, by Mercuriali, published at Venice in 1601, the author attributes the disease to perverted humours, and says it is contagious because the liquid containing the contagious principle is deposited on or in the skin.