11 APRIL 1969, Page 28

Dog days

Sir : J. W. M. Thompson (`Spectator's note- book,' 4 April) asks for the origin of 'black dog' as another name for depression. Milton ('L'Allegro') derives 'melancholy' from `Cer- berus and blackest midnight.' Cerberus was the watchdog of Hades and was certainly black (see Tibullus, 1, 3, 71), with a tendency to devour people; and the description of the huge Molossian in Lucretius (De Rerum Natura 5, 1063) makes me feel that is the real dog referred to. Unlike the modern Labrador, the black Molossian was fierce and used as a watchdog, and there may have been a legend connecting Hades himself with the Molossians. Another possibility is that the reference is to Hecuba, wife of Priam, who was turned into a bitch after avenging the death of her youngest son Polydorus, but Ovid gives no colour in his Metamorphoses.