Public policy forbids the maintenance of any suit in a court of justice, the trial of which would inevitably lead to the disclosure of matters which the law itself regards as confidential, and respecting which it will not allow the confidence to be violated. On this principle, suits cannot be maintained which would require a disclosure of the confidences of the confessional, or those between husband and wife, or of communications by a client to his counsel for professional advice, or of a patient to his physician for a similar purpose. Much greater reason exists for the application of the principle to cases of contract for secret services with the government.