Already in Homer imagination had been caught by the total distinctness of the mode of life which was followed by the nomads of the North; and a vague connexion had been felt between the purely pastoral existence and a peculiarly orderly habit of life and behaviour. A fragment of Choerilus, whom those who had access to his work felt to stand in some peculiarly close relation to Herodotus, connects these two qualities explicitly;[108] and the same thought recurs twice over in that storehouse of anthropological learning, the _Prometheus Solutus_ of Aeschylus.[109] In the latter passage it would be forcing the literal sense of the words unduly, to insist that the Gabii are to be pictured as living on wild corn, especially as Greek theory was at all other points unanimous that corn, like the olive and the vine, came to man by special providence as something ἡμερον φύσει. The Aeschylean picture clearly is that of the virgin soil of the trans-Euxine grassland, where the spring vegetation will endure comparison with any merely Aegean cornland. There is enough in this single example to show that the men of the early fifth century were already aware of the inter-dependence of environment, economy, and institutions. For the generation of Socrates, we have the treatise of Hippocrates already mentioned, ‘On Air, Water, and Places’; of which the whole burden is, as we have seen, that not only men’s social organization, but their very physique, is the result of ‘acquired variations’ initiated by the climate and economic régime. I hinted, a little earlier, that there is another reason why Herodotus should pay close attention to the peculiar food of strange peoples. That different kinds of food-quest should lead to different manners and institutions was probably, even in the fifth century, a less familiar conception than that the personal qualities of the individual depended directly on the food which he ate. This is of course a matter of elementary knowledge to most savages; it is an explicit principle of the medical doctrine of Hippocrates; it has had the profoundest influence on the vocabulary and ritual of great religions, and it has by no means disappeared from the current thought of mankind; it is still believed, by otherwise intelligent people, that the morals of nations may be mended, by defining the quality of their food and the quantity of their drink. With this conception in mind, we shall cease to be surprised that Herodotus devotes so much time and care to describe the preparation of plum-cake, or kirschwasser, or beer. Man might not live by bread alone; but if you once were certain that a man did live on bread, and not on monkeys, or on lice, you knew already a good deal about the habits and the value of that man.