78 GREEK AND ROMAN MYTHOLOGY he is the son of Apollo, the god of healing, but is in- structed in the healing art by the wise Centaur, Chiron. Since by his art he even calls back the dead to life, the god of the lower world complains of him to Zeus, and the latter thereupon slays him with a stroke of lightning. His children are the physicians Machaon and Podalirius, and the personifications of health and healing, Hygea (' health'), laso (' healing'), Panacea ('cure-all/ ' remedy for everything'), and Aegle ('the shining one/ 'the won- derful '). Aesculapius is usually represented as a kindly, wise-looking man, standing, and with all the upper part of his body bare, except the left arm and shoulder. He carries as a symbol a large staff, entwined with a ser- pent, and often wears a headband. Aesculapius: Homer, II. iv. 194; Hyginus, Fab. xlix. ; Shak., Pericles iii. 2, 111 : , And Aesculapius guide us ! Spenser, F. Q. i. v. 41. Machaon : Homer, II. ii. 732 ; Ovid, Ex Pont. i. 3, 5. Aegle : Vergil, Eel. vi. 21 : Aegle, Naiadum pulcherrima. Shak., Midsummer Night's Dream ii. 1, 79. IV. PERSONIFICATIONS 104. As men's conception of the gods gradually becomes spiritualized, such forces as are not directly perceptible through the senses, but are rather of a purely spiritual nature, whose effect is manifest as well in private as in public life, are attributed to the activity of independent divinities. Thus that which we "know as a mere abstract idea acquires a personal form. So are developed (1) the friendly divinities of love, social intercourse, order, and