Each commissioned officer before entering upon the duties of his appointment shall take and subscribe the following oath: "I, .........., do solemnly swear that I will support and defend the Constitution of the United States and the Constitution of the Commonwealth of Pennsylvania against all enemies; that I will bear true faith and allegiance to the same; that I will obey the orders of the Governor of the Commonwealth of Pennsylvania; that I make this obligation freely without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office .......... in the Pennsylvania Guard upon which I am about to enter."