The parol evidence rule presupposes an action based on a valid contract, and between the parties thereto or those claimmoney of the estate in a bank, taking a certificate of deposit, was not allowed to show a contract between himself and the bank permitting him to withdraw the money at any time to relieve himself from liability after the bank had failed.

8 Folinsbee v. Sawyer, 157 N. Y. 196; 51 N. E. 994.

9 Harvey v. Henry, 108 la. 168; 78 N. W. 850.

10 Elliott v, S. S. Co., 22 Wash. 220; 60 Pac. 410.

11 Walker v. State, 117 Ala. 42; 23 So. 149.

12Andrus v. Blazzard, 23 Utah 233; 54 L. R. A. 354; 63 Pac. 888.

13 Sayre v. Burdick, 47 Minn. 367; 50 N. W. 245; Schneider v. Kirkpat-rick, 80 Mo. App. 145.

14Schultz v. Bank. 141 111. 116; 33 Am. St. Rep. 290; 30 N. E. 346; Traders' National Bank v. Water-Power Co., 22 Wash. 467; 61 Pac. 152.

15O'shea v. Ry.. 105 Fed. 559; 44 C. C. A. 601.

ing under them. If the issue is as to the existence or validity of the contract, the rule by its very terms has no application and extrinsic evidence is necessarily admitted to determine such issue, whether such evidence tends to establish the validity1 or the invalidity2 of the contract in question. Specific instances of the application of this principle will be given in the following sections.