“menstruum /ˈmɛnstruəm/ (men-stroo-əm), rarely written also “menstruüm”, is an archaic term for a solvent, i.e. a liquid that dissolves a solid.”
I thought that happened monthly?
;)
That’s right! That was in C.S. Lewis’s “The Pilgrim’s Regresss”
A skeptical character told another one that having eggs for breakfast was “eating the menstruum of a verminous fowl”...