The same benefit which the medicinal principle developed by itself works in its own constitution it confers upon man when subjected to the same evil. And so it is with all the herbal medicines. They have a purpose to serve in the economy of the plant that yields them before they can minister to human sickness and disease. Sugar was not meant in the first instance to sweeten man's cup, but to store up food for the plant in order to enable it to flower. Tannin is created in the bark of the oak tree, in the first instance, not for the purpose of helping to make leather for man's shoes, but for the purpose of preventing mildew and fungous growths from settling on the bark of the tree and so decaying it. Scent is produced in flowers and shrubs that grow in watery places, not for man's gratification in the first instance, but in order to deodorise the air and make it fit for these scented flowers and shrubs to breathe and to preserve their vitality and vigour. Aromatic fragrance is yielded by the grey shrubs and herbs of the dry desert, not that the garments of the human passer-by might smell pleasantly of it, but that it might regulate the temperature, and keep the plants cool in the burning heat of the noonday and warm in the freezing cold of the night air. Such instances might be multiplied indefinitely. Indeed, it may be regarded as a rule of nature without exception that, whatever properties plants possess that are useful to man, these properties, in the first instance, are not only useful but indispensable to themselves. And it is because they serve necessary uses in their own economy that they are found so necessary in the economy of man. Each plant that grows in circumstances where it is likely to be injured by the soil or climate develops within itself the antidotes and remedies against these unfavourable circumstances. It is a physician that heals itself first of all, that adapts itself as perfectly as possible to the peculiarities of its own place of growth. Nature and it are harmonious: they help each other. The qualities that are beneficial to itself are equally in the same way beneficial to other creatures; and it helps the world because it has first helped itself. It imparts health all around because it looks first after its own health.