The earlier ancient authors appear to have entertained no suspicions of contagion as a cause of febrile or of other complaints. Homer, as formerly stated, evidently refers the origin of the plague which prevailed in the Grecian army during the siege of Troy to the heat of the sun. The works of the fathers of History and of Medicine have likewise been ransacked in vain, for any traces of the doctrine of contagion. Thucydides, therefore, appears to be the first author (if we except the Mosaic description of leprosy) who makes any positive allusion to the contagious nature of diseases. From his description of the plague of Athens, there can be no doubt that he wishes it to be understood, that the disease was transmitted from one person to another; for he mentions that physicians were more attacked by it than any others, as having most intercourse with the sick; and he afterwards describes the terror which the citizens felt to approach those labouring under the disease, and intimates that it was often contracted by such intercourse. The language of Lucretius, who copies his description, and gives it a poetical form, is still more precise:— “——nullo cessabant tempore apisci Ex aliis alios avidi contagia morbi.” (L. 1235.) And afterwards, “Qui fuerant autem præsto contagibus ibant.” (L. 1241.) Ovid, in like manner, says of the dead bodies: “Afflatuque nocent et agunt contagia latè.” (Metam. v, 551.) And so also, Silius Italicus: “Et posuere avidæ mortis contagia pestes.” (Lib. xiv.) The historians we must dismiss in a few words, with stating that allusions to the infectious nature of certain diseases are to be met with in Livy, Dionysius the Halicarnassian, Diodorus Siculus, Appian, Plutarch, Quintus Curtius, Dio Cassius, Eusebius, Gregory of Nyssa, and Evagrius. Procopius was a non-contagionist. The philosopher Aristotle, in one of his problems, makes it a question why the plague is the only disease which infects those who approach the sick. (Probl. i.) There is a curious passage in the works of the orator Isocrates, which shows that consumption was reckoned contagious in his days. (Æginet.) The elder Pliny mentions the contagion of the pestilence. (Hist. Nat. xxxiii, 80.) Virgil mentions the infectious nature of certain diseases of cattle. (Ecl. i, Georg. iii, 464.) The ancient writers on veterinary surgery and agriculture in like manner state that the plague and scabies of cattle are infectious. See Columella (vi, 5); Vegetius (Mulomed. iii, 23.)