In the 19th century, physicians and public-health officials began to understand disease-transmission vectors with more precision, even though germ theory did not triumph until near the end of the century. Particularly in Western Europe, health reforms inspired large urban public works to deal with waste. Government officials inventoried communities, especially where there were concentrations of urban poor. Not surprisingly, they found huge piles of garbage, including human and animal waste, in the streets.

Edwin Chadwick’s 1842 “Report on the Sanitary Condition of the Laboring Population and on the Means of its Improvement” describes the era’s conflicting excremental economies with shock and disdain:

There were no privies or drains there, and the dung heaps received all filth which the swarm of wretched inhabitants could give; and we learned that a considerable part of the rent of the houses was paid by the produce of the dung heaps. Thus, worse off than wild animals, many of which withdraw to a distance and conceal their ordure, the dwellers in these courts had converted their shame into a kind of money by which their lodging was to be paid.

Chadwick’s laboring population was primarily urban, but 19th-century America retained much of its Jeffersonian, agrarian nature. As a result, excrement had a different value in the New World. In 1853, D.J. Browne published The Field Book of Manures (also called The American Muck Book). He devotes a chapter to dog feces, noting that “this manure, wherever it could be obtained in sufficient abundance, has been found to be, it is stated, the ‘most fertile dressing of all quadruped sorts.’” Browne goes on to describe an 18th-century English farmer from Bedfordshire with an abundance of setters and spaniels. Their dung reportedly enabled his gravelly fields to outperform those of his neighbors. He also describes the valuable “corrosive” power of white dog dung, which he attributes to a carnivorous, bone-heavy diet.

Such white dung is the probable source of the appellation “dog lime.” It is likely Williams’s old man with the majestic tread was not cleaning up after his pet like the modern dog walker, but gathering dog lime for his garden. As a result, it probably had a yield superior to his neighbors who did not stoop to such indignity.

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During the 20th century, Western attitudes toward dog ordure shifted. The world is still full of dogs, but owners now fear the diseases this once-useful commodity represents. The triumphs of Joseph Lister, Louis Pasteur, and their fellow germ theorists explain part of the aversion, but not all of it. Industry had a greater role to play in the retirement of animal waste.

For alchemists, dung heaps provided chemicals and constant temperature. But modern chemists made the dung heap obsolete by producing synthetic alternatives. The change began with Friedrich Wöhler’s synthesis of urea in 1828, the first organic compound produced from inorganic compounds. Wöhler’s work paved to way for the Haber process, an industrial-scale ammonia-production method, and the birth of the modern fertilizer industry. (Fritz Haber is also known for managing the laboratory that developed Zyklon B, initially for use as an insecticide, later deployed by the Nazis in their death camps.)