Philosophy in those days was regarded as incomplete unless it included some knowledge of natural phenomena, to be used for purposes of analogy. Origen and Athanasius display a considerable interest in, and acquaintance with, physical and physiological matters, and Hilary shares the taste. The conditions of human or animal birth and life and death are often discussed E.g. Trin. v. 11, vii. 14, ix. 4.; he believes in universal remedies for disease Trin. ii. 22., and knows of the employment of anæsthetics in surgery Trin. x. 14. This is a very remarkable allusion. Celsus, vii. præf., confidently assumes that all surgical operation must be painful.. Sometimes he wanders further afield, as, for instance, in his account of the natural history of the fig-tree Comm. in Matt. xxi. 8. and the worm Trin. xi. 15., and in the curious little piece of information concerning Troglodytes and topazes, borrowed, he says, from secular writers, and still to be read in the elder Pliny Tract. in Ps. cxviii. Ain. 16; it is from Plin. N.H. 37, 32.. Even where he seems to be borrowing, on rare occasions, from the commonplaces of Roman poetry, it is rather with the interest of the naturalist than of the rhetorician, as when he speaks in all seriousness of ‘Marsian enchantments and hissing vipers lulled to sleep Tract. in Ps. lvii. 3. It suggests Virgil, Ovid, Silius, and others.,’ or recalls Lucan’s asps and basilisks of the African desert as a description of his heretical opponents Trin. vii. 3.. Perhaps his lost work, twice mentioned by Jerome Ep. 70, 5, Vir. Ill. 100., against the physician Dioscorus was a refutation of physical arguments against Christianity.