Because Who Wants Impure Blood?

"CRAYFISH-BROTH FOR PURIFYING THE BLOOD.  Take two pounds of the lean part of very white veal, chop it very fine; add to it three dozen crayfish and a handful of green chervil; pound them together to thoroughly bruise the crayfish; then put the whole into a stewpan and pour upon it three pints of cold spring water;  add a little salt, and place the stewpan on the stove to boil.  After half an hour, set it back on the stove, and let it simmer very gently for an hour, then strain.  It should be taken fasting to insure its best effect."

La Cuisine Creole, 1885, by Lafcadio Hearn (of all people).  Available as a free download from the MSU site, Feeding America.