The consideration which is agreed to be paid by the purchaser of a thing in money. It is the duty of the purchaser to pay the purchase-money as agreed upon in making the contract, and, in case of conveyance of an estate before it is paid, the vendor is entitled according to the laws of England, which have been adopted in several of the states, to a lien on the estate sold for the purchase-money so remaining unpaid. This is called an equitable lien. This doctrine is derived from the civil law. The case of Chapman v. Tauner, decided in 1684, is the first where this doctrine was adopted. It was strongly opposed, but is now firmly established in England, and in the United States.
But the lien of the seller exists only between the parties and those having notice that the purchase-money has nut been paid.