`Learn from me, my son, what are hunger and thirst. When a man is thus said to be hungry, water is carrying away (digests) what has been eaten by him. Therefore as they speak of a cow-leader (go-naya), a horse-leader (asva-naya), a man-leader (purushanaya), so they call water (which digests food and causes hunger) food-leader (asa-naya). Thus (by food digested &c.), my son, know this offshoot (the body) to be brought forth, for this (body) could not be without a root (cause).