Disability of a plaintiff to sue does not go to the merits of an action, and can be taken advantage of, in pleading, only by plea in abatement. After answer to the merits, proof of the disability at the trial will not avail the defendant. Hay-den v. Attleborough, 7 Gray, 338. Jaha v. Belleg, 105 Mass. 208. Objections to the form of the action or to the pleadings are not open in a case submitted on an agreed statement of facts, unless *181specially reserved. Such submission waives all technical objections, and raises only the -.question whether the plaintiff can recover in any form of action, though the pleadings are referred to. Kimball v. Preston, 2 Gray, 567. Cushing v. Kenfield, 5 Allen, 307. West Roxbury v. Minot, 114 Mass. 546. When a case is thus submitted, the plaintiff may amend his writ or declaration in any way necessary to put his case in proper form to support the judgment to which the facts entitle him. Merrill v. Bullock, 105 Mass. 486. Folger v. Columbian Ins. Co. 99 Mass. 267. The irregularity in prosecuting this action by the infant plaintiffs in their own names, and without the intervention of a prochein ami, could have been amended if it had been pleaded in abatement; Blood v. Harrington, 8 Pick. 552; and must therefore be regarded as waived by the defendant. It would undoubtedly be more regular that any judgment for the plaintiffs should be rendered in their favor as suing by a next friend, and they ought, before judgment is entered, to obtain leave in the Superior Court to amend their writ accordingly.
The St. of 1871, e. 382, under which the betterment was assessed on the estate, provides, in § 6, that all assessments made under it shall constitute a lien on the real estate so assessed, to be enforced in the same manner, and with the like charges for cost and interest, as provided by law for the collection of taxes. It is contended by the defendant, that by the force of this provision an assessment-of betterment is void, if, in addition to being made on the proper estate, it is made to one who is neither owner nor occupant of the estate. This would be so if the statute required the assessment to be made to the owner or occupant. Desmond v. Babbitt, 117 Mass. 233. But it was held in the case of Alvord v. Collin, 20 Pick. 418, that, where an assessment on unimproved land of a non-resident was made to a former owner, the tax was legally assessed; the question arising under the St. of 1785, c. 50, which did not require non-resident owners to be named in the assessment. The distinction between that case and one arising under the Gen. Sts. e. 11, § 8, is pointed out in the opinion of the court in Desmond v. Babbitt, ubi supra. The clause of the St. of 1871, relating to the manner of enforcing the lien created by the assessment of betterment, refers only to proceedings subsequent to the assessment, and has nothing to do *182with the making of it. The assessment on the land of which the defendant owned one undivided fourth part was, therefore, properly made, and constituted a lien on the land. That such lien became an incumbrance from the time of passing the order to widen the street, is settled. Blackie v. Hudson, 117 Mass. 181. Carr v. Dooley, 119 Mass. 294. There has been, therefore, a breach of the covenant against incumbrances, for which this action may be maintained. It remains to be considered what amount of damages the plaintiffs are entitled to.
The general rule is, that the covenantee who has removed the incumbrance may recover the reasonable expense of doing so, not exceeding the value of the estate. Norton v. Babcock, 2 Met. 510. Harrington v. Murphy, 109 Mass. 299. Johnson v. Collins, 116 Mass. 392. If he has not removed it, or has removed it without expense, he is entitled to nominal damages only. Prescott v. Trueman, 4 Mass. 627. Tufts v. Adams, 8 Pick. 547. The amount which he may recover is the fair and reasonable amount expended in good faith. Farnum v. Peterson, 111 Mass. 148. It must be understood to be a price just and reasonable as against the covenantor, and not exceeding what he would have been bound to pay. Norton v. Babcock, ubi supra. The assessment was a lien on the whole land. The defendant conveyed one undivided fourth part, with covenant against incumbrances. The plaintiffs bought the other three fourth parts, subject to the incumbrance, and by deed without the covenant. They stand toward the defendant,- therefore, as if they had been her cotenants when the incumbrance was put upon the land. If she had removed it, they could have been compelled to pay her three fourths of the amount paid in so doing. If they had removed it, they could have recovered one fourth of the expense from her. Dickinson v. Williams, 11 Cush. 258. The incumbrance, when the defendant conveyed, was, as between her and her cotenants, one fourth of the assessment; because, though it was an incumbrance on the whole and on every part of the land, she would have had an action against them for what she paid in excess of her proportion of the whole. The plaintiffs cannot, therefore, be regarded as having paid the whole assessment for the purpose of removing the incumbrance from the one fourth of the land which the defendant owned in common with them. Such pay*183ment would not be in good faith, would not be reasonable toward her as the covenantor, would be more than, as between her and the plaintiffs, as her cotenants, she would have been obliged to pay. To hold otherwise would be doing not so much injustice in dollars and cents, but precisely the same injustice in principle, as to hold that the plaintiffs paid the whole amount to remove the incumbrance from the three fourths of the land which the defendant did not convey to them.
We think, therefore, that it was error in the Superior Court to order judgment for the whole amount of the assessment; and, according to the terms of the agreement, judgment must be entered for the sum of $191.25, and interest from the date of the writ. Judgment for the plaintiffs accordingly.