A 1910 British medical article about Spanish medical folklore includes some stories about how to induce milk:
“Spanish Medical Folklore,” British Medical Journal, October 15, 1910, p. 1168. The unsigned article explains that its information comes from “two articles on Spanish superstitions, by Dr. Martin arrera y Dellunder, which appeared in the Gaceta Medica Catalana of February 15th and March 15th, 1910.”says:
“If there is difficulty in getting the milk to flow, the Spanish woman has many methods to induce it. One very quaint one is to put on her husband’s shirt immediately after he has taken it off. Another way is tot suckle two children at once, and yet another to squirt the milk on to the wall, or into the flame of the candle which lights the room, so that it may burn. Another method is to use fomentations of sage boiled in urine, or to place a hollow key filled with mercury between the shoulders. In certain districts of Valencia there is a curious belief that the milk of the woman may be drawn out by means of feeding a cat or a dog on the bones of a fowl which has been made into soup.”