Parmentier and Deyeux (1799): donkey milk in an early milk comparison

Background

Who, when, what kind of text

Parmentier, known as the promoter of the potato in France, and the apothecary Deyeux submitted a prize essay to the Société royale de médecine in 1788. The question was to determine the nature of the milk of women, cows, goats, she-asses, ewes and mares by comparative physical and chemical investigation. They expanded the prize-winning work into this book.

Around 1800, chemistry was in its infancy: milk was separated into cream, butter, “cheesy matter”, whey and “milk salt” (milk sugar), but proteins in today’s sense could not yet be determined. The authors themselves stress that exact quantities were not possible because of the variations between animals.

Content

What the source reports about donkey milk

In the chapter “Du lait d’ânesse” (pp. 260–264), the authors describe donkey milk as similar to human milk in colour, taste and consistency, but chemically distinguishable. The cream was never thick or abundant, and the butter obtained from it soft and white. Acids and alcohol caused the cheesy matter to precipitate in very fine particles instead of a solid mass as with cow’s, sheep’s and goat’s milk.

For milk sugar, they observed clear differences between the animals: three equal portions from three she-asses each yielded noticeably different amounts. The milk sugar obtained was the same as that of human and cow’s milk.

A practical observation (pp. 207–208): when a she-ass was led from house to house and milked for several patients in succession, the first received the most watery milk and the last the fattiest. The authors therefore suggested milking once and dividing the yield.

In the ranking table at the end (p. 418), they rank the six types of milk: for whey content (“sérum”) the she-ass comes first, for milk sugar (“sel essentiel”) second, and for butter and cheesy matter near the bottom. They group human, donkey and mare’s milk together as a separate group.