Historical label: “Flux” in the 1850 edition’s “A List of the Principal Diseases”.
Modern literature has not yet been searched for this heading’s claims: it comes only from the 1850 index and has no search words yet.
A note on the heading
Plain sense
A flow out of the body. Narrowly the “flux or lask of the belly”, diarrhoea; widely, as in Bistort’s sentence, any flow, blood included.
What the entries treat
Three claims: two sentences and an index name. Flux-weed, named for it, “to stay the flux or lask of the belly, being drank in water wherein gads of steel heated have been often quenched”; Bistort’s root “stays all manner of inward bleeding, or spitting of blood, and any fluxes in the body of either man or woman, or vomiting”. Rhubarb of Pontus (p. 225) is an index name the book has no entry under. The bloody flux has its own heading (CND-0016), and the fluxes of blood are under Bleeding (to stay) (CND-0013).
Where the word comes from
Old French flux, from Latin fluxus, “flow”. Lask, its partner in Flux-weed’s sentence, is from Old French lasche, “not taut or tight, limp”, and Wiktionary’s quotations for it include Culpeper himself in 1652: “staieth Lasks and continual Fluxes”.
Today’s words
diarrhoea; (widely) any discharge or bleeding — a broad match: the heading covers more than this, or several modern things.
How it reads today
“Flux” now lives in physics and in “in flux”; the medical sense is archaic. Read it as diarrhoea first: that is Flux-weed’s “flux or lask of the belly”, and Wiktionary’s first medical sense. Bistort’s “any fluxes in the body” is the wide sense, and that half belongs with Bleeding (to stay).
References
Wiktionary, s.v. “flux” (accessed 2026-10-28): from Old French flux, from Latin fluxus “flow”; senses “(archaic) an illness causing diarrhoea, especially dysentery” and “(archaic) diarrhoea or other fluid discharge from the body”, Milton 1670 “strange fluxes upon men”. Wiktionary, s.v. “lask” (accessed 2026-10-28): from Middle English laske “lax, weak; of the bowels: loose”, from Old French laske, lasche “not taut or tight, limp”; sense “looseness of the bowels; diarrhoea”, with the usage note “Originally of both persons and animals, now only of animals”; quotations Gerard 1597, Burton 1624 and Culpeper 1652, “The Emulſion or Decoction of the Seed ſtaieth Lasks and continual Fluxes”.
ThinkDeep333, 2026-10-28 · draft, not yet checked. Offered beside Culpeper’s heading, never in its place; nothing here says whether a plant works.
Old claims, quoted verbatim: not medical advice. A warning sits above the claims and never hides them; no warning does not mean safe, only that no source here has flagged the plant.
3 claims: 2 with a sentence, 1 from the index alone
The root in powder, the decoction thereof in wine being drank, stays all manner of inward bleeding, or spitting of blood, and any fluxes in the body of either man or woman, or vomiting.
Flux-WeedDescurainia sophiaCLM-0023151850 index, p. 78
Both the herb and seed of Flux-weed is of excellent use to stay the flux or lask of the belly, being drank in water wherein gads of steel heated have been often quenched;