Certain general counts, not founded on any special contract, which are introduced in a declaration, for the purpose of preventing a defeat of a just right by the accidental variance of the evidence. These are in an action of assumpsit; counts founded on express or implied promises to pay money in consideration of a precedent debt, and are of four descriptions: 1. The indebitatus assumpsit; 2. The quantum meruit; 3 . The quantum valebant; and, 4. The account stated.