Old School Laxatives!

Up until about 1750, people who were "plugged up" drank Castor oil. That was the name of a liquid laxative that was extracted from the glands of a beaver (or Castor, in Latin).

So my question is this: 

Whose idea was it to drink liquids extracted from the glands of a beaver?!

(BTW, after the mid-1700s, it was discovered that the same laxative effect could be got from the oil produced by the seeds of Ricinus communis, which became known as the castor oil plant. Oh, and that photo is by Paul Stevenson.)