The appointment of a guardian ad litem to appear and answer for the respondent necessarily presupposes that in a previous stage of the case her mental condition and capacity had been inquired into and the fact of her insanity during the pendency of the suit duly ascertained and adjudicated. Formerly the power to appoint a guardian in such cases was not exercised by the court; but upon suggestion that the respondent was insane, the party prosecuting the libel, as preliminary ff> a *266hearing on the merits, was required to procure the appointment of a guardian in the probate court. Mansfield v. Mansfield, 13 Mass. 412. By the Rev. Sts. c. 76, § 18, it is provided that “ if the respondent is insane, at any time during the pendency of the suit, the court shall appoint some suitable person as a guardian.” This provision clearly requires the court to determine judicially the fact of the insanity of the respondent, as a condition precedent to the exercise of the authority to appoint a guardian ad litem. Such determination is in the nature of an interlocutory decree or judgment in the case. It establishes the fact of the existence of insanity in the respondent during the pendency of the suit, and, being the judgment of a competent tribunal on the question, it is prima facie evidence of the fact in any subsequent stage of the case. Besides, insanity, when once proved, is presumed to continue unless it was accidental or temporary in its nature, which is not alleged to be in the present case. Stone v. Damon, 12 Mass. 488. Breed v. Pratt, 18 Pick. 115. Hix v. Wliittemore, 4 Met. 545.

As the case stood, therefore, when the libellant offered to testify, the presumption was that the respondent was still insane, and in the absence of proof to the contrary on the part of the libellant, he was not a competent witness, if the case falls within the exception to St. 1857, c. 305, § 1, which provides that when one of the original parties to the contract or cause of action then in issue and on trial is shown to the court to be insane, the other party shall not be admitted to testify in his own favor.

There would seem to be no room for doubt that the case at bar falls within this exception. Whatever question or controversy may exist among legal writers and jurists concerning the nature of the relation subsisting between husband and wife after marriage — whether the rights and liabilities of the parties are then to be regulated and governed by the principles applicable to all civil contracts, or the contract is to be considered as merged in the higher nature of the status created by the agreement of the parties — all the authorities concur in the conclusion that marriage has its origin and foundation in a purely civil *267contract. 2 Kent Com. (6th ed.) 76, 86. Shelf. Mar. & Div. 1. Edmonstone’s case, Ferguson, 397—399. Milford v. Worcester, 7 Mass. 52. Smith v. Smith, ante, 210. The whole object of the present suit was to annul and cause to be declared void that contract, which the parties had in form and according to legal usage assented to, upon the ground that the respondent was wanting in capacity to enter into a valid contract at the time the marriage ceremony was solemnized. The existence and validity of the contract was directly “ in issue and on trial.” The case was therefore within the express words of the statute. It was also within its spirit. The object of this clause in the statute was to prevent the gross injustice of allowing one party to a suit to testify to facts equally within the knowledge of both, when the other party was incapacitated from giving testimony in a court of justice.

For these reasons, a majority of the court are of opinion that the libellant was not a competent witness and his evidence should not have been received at the trial. Verdict set aside.