One farmer says to me, “You cannot live on vegetable food solely, for it furnishes nothing to make bones with”; and so he religiously devotes a part of his day to supplying his system with the raw material of bones; walking all the while he talks behind his oxen, which, with vegetable-made bones, jerk him and his lumbering plow along in spite of every obstacle. Some things are really necessaries of life in some circles, the most helpless and diseased, which in others are luxuries merely, and in others still are entirely unknown.

Henry David Thoreau, Walden