This section of the book is from the "Household Companion: The Model CookBook" book
Sterilize milk bottles or jars by boiling them twenty minutes in water. Remove them, fill two-thirds full of milk, and cork with baked or prepared cotton or with rubber corks which have been sterilized. Place the bottles on a wire stand in a kettle of cold water, heat the water gradually to 165 degrees Fahrenheit, and keep it at that temperature forty minutes; then remove the bottles and cool quickly by placing them in cold or iced water. Keep the bottles in a cool place.
A thermometer for testing the temperature may be bought at any pharmacy, but if there is none at hand heat the milk until a scum forms over the top, and keep it as nearly as possible at that temperature for forty minutes. Do not allow it to boil.