A hundred years ago this month, the February 1919 issue of Popular Science showed this simple device for skimming milk. It consisted of a glass tube and a rubber lid for the milk bottle. While the principle was not explained, it appears that the tube rests in the top layer of cream. When pressure is applied, the cream is dispensed through the tube.

For those too young to understand the concept, milk straight from the cow is not homogenized.  This means that if the bottle is left to stand, the cream will rise to the top, and the skim milk will settle to the bottom.  This device allows you to “skim” the cream, hence the name of the liquid left over.