TYSON, C. J.

This case was before the court on a former appeal, and is reported in 147 Ala. 367, 41 South. 1025. On that occasion it was held that pleas 4 and 5 were sufficient. These pleas set up, as an estoppel against the relief prayed, that appellant had induced the defendant to undertake the work complained of and to incur pecuniary liabilities therefor. On the return of the case to the lower court the bill was amended, and went into greater details as to the injurious consequences of the change of the grade of the street, and made averments to meet the allegations of these pleas. Said pleas 4 and 5 were then amended, and a new plea, No. 7, filed, and, the case being submitted as to the sufficiency of these pleas, the chancellor sustained them, and this appeal is to reverse that decree. The question, therefore, on this appeal, is as to the sufficiency of said pleas 4, 5, and 7 to' the bill as amended. We refer to the report of this case and the opinion pronounced in it for a full statement of the points involved.

Pleas 4 and 5 as then taken, and now, with the added plea 7, may be regarded, as setting up the same defense, to wit, the estoppel in pais then considered and held to be sufficient. The essential nature and requirement of a plea at law or in equity is that it shall completely answer the bill, at least to the extent that it purports to be a defense; and therefore, if any material allegation is not negatived by a, traverse or confession and avoidance, it is necessarily taken as true in considering the plea, and will render it bad. — 16 Cyc. 228; McCay, etc. v. So. Bell Tel. Co., 111 Ala. 351, 19 South. 695, 31 L. R. A. 589, 56 Am. St. Rep. 59. “The aver-ments of a plea must be certain, precise, and such as are necessary to avoid all ambiguity of meaning and exclude all intendments. * * * If we allow the averment to he true, but at the same time a case may be supposed con*655sistent with it which would render the averment inoperative as a full defense, such a case will he presumed or intended, unless excluded by particular averments.”— Whitlock v. Fisk, 3 Edw. Ch. (N. Y.) 131. The matter in the plea must be a complete bar to the equity in the bill. — Rhode Island v. Massachusetts, 14 Pet. (U. S.) 271, 10 L. Ed. 423. The fundamentaly doctrine of an estoppel in pais is well stated in Jones v. McPhillips, 82 Ala. 115, 2 South. 468. It is conduct intended and calculated to induce, and in fact inducing, another person to alter his condition, so that it would be a fraud upon him to allow the other party to take an inconsistent attitude to his detriment. — Leinkauff v. Munter, 76 Ala. 194; Ware v. Cowles, 24 Ala. 446, 60 Ain. Dec. 482; Henshaw v. Bissell, 18 Wall. (U. S.) 255, 21 L. Ed. 835. Mr. Bigelow says: “Conduct, as the basis of an estoppel, must have been intended for the other party to act on, and he must have been induced to act upon it.” Bigelow on Estoppel, 570.

The estoppel allowed on the former appeal was that the complainant, with full knowledge of the proposed improvement and change of grade of the street, consented thereto-, and requested the city officials to proceed with this work; that they were induced to act, and did act, on this request and consent, and incurred liabilities and expenses. These circumstances were alleged as sustaining this plea: One, that the complainant had petitioned defendant to have the stréet improved; another, that defendant was advised by skillful engineers that the improvement should be after the plan adopted as to grade of streets; and, third, that “after said grade had been raised and established, as it now is, one of defendant’s councilmen, a member of the street committee, having said work under supervision, went to complainant and advised him of the change of said grade, and the *656said complainant- told said councilman to go ahead and do the work on the grade established, that he was going to raise his house anyway, and that he wanted the street fixed right, * * * and that this defendant, acting upon said proposition * * * and of said declaration and consent,” did the work and entered into obligations for work and labor, etc. The petition set out in the pleas had no suggestion as to how the improvement was to be made, nor contained any express or implied waiver of damages on the part of the signers arising from the improvements actually made; and the bill, after amendment, shows that it was presented in July, 1903, and that nothing was done in regard to the matter until May, 1905, when an ordinance was introduced and passed for. paving a part only of the avenue, and providing for the assessment of costs and expenses on a different plan from that mentioned in the petition. We held on the former appeal that the petition referred to did not, as originally pleaded, create any estoppel against complainant; and in the light of the amended bill, showing that it was not acted on and accepted as proposed, or when proposed, if at all, or within any reasonable time thereafter, the conclusion we then reached becomes stronger on this appeal.

There is no connection shown, other than by the mere conclusion of the pleader, between the action of the municipal authorities and the petition set out for the improvement of the street. They appear to be two independent and totally disconnected facts,, which are impossible to be related as cause and effect. As to the circumstance that the defendant was advised by competent engineers that the work had to be done as proposed and done, or that it was proper work and could be done only in that particular way, it seems obvious that such matters, singly or in connection with the petition for the improvement set out in the plea could not assist *657to bnilcl up a waiver of the constitutional right to compensation for damages resulting from appropriating private property for public purposes. If the action complained of was not induced by the petition, as on the allegations of the 'hill it could not have been, its importance could not be increased by its conjunction with the subsequently developed fact that the work was done in the only scientific method possible.

We come, then, to the last circumstance alleged against the appellant in support of the pleas. On the former appeal the pleas were made to affirm that the proposition of improving the street in the manner complained of was communicated to complainant by the defendant’s agent, with suggestions of change of one inch in the height of grade, in the plan, if desired; that appellant approved the plan and requested the agent to go ahead with the grade as proposed, and the plea was construed to aver that the defendant was induced to act, and change its position, and undertake the work, and incur liabilities by this conduct of the appellant; and on that assumption we held pleas 4 and 5 sufficient. But on return of the case to the lower court the bill was amended so as to aver that, when the alleged conversa.tion -with defendant’s agent occurred, the defendant had already entered into all its contracts and incurred all its liabilities respecting the improvement of the street at the established grade, which it was advised was the lowest possible elevation, and that soon after said conversation appellant appeared before the board of mayor and aldermen of the town in open session, and asked relief ‘by reason of the injuries arising from the elevation of the grade of the street, which was denied, and that between the said conversation and the said complaint and denial of relief the defendant entered into no contract and incurred no- new liability. And then the bill *658further states what said conversation was, and the circumstances under which it occurred. The hill denies that complainant consented to- the grade, but admits that he rejected the suggestion of lowering the curb,, because at the elevation of the street a lower curb1 would be ineffective, and that he admitted that he said he was going to raise his house, but it was because it was a necessity from the elevation of the grade of the street, and that he said nothing further than that under such circumstances two or three inches would make no difference, and that he wanted it fixed right while they were fixing it.

Pleas 4 and 5, as amended, and plea 7, as filed, admit all these allegations of the bill as amended — that is, that the only substantial fact supporting the estoppel occurred after the defendant had entered into its engagements; that if the conversation referred to was calculated to induce the defendant to alter its position, and had been communicated to it, which is not alleged it was retracted before defendant in fact altered its position; and, finally, that the conversation occurred in the mode and manner, and under the circumstances and to the effect, detailed in the bill, which show that it was not intended to induce, and was not calculated to induce, the defendant to alter its position, and that it did not, singly or in conjunction with any other matter, cause the defendant to appropriate or injure appellant’s property in violation of the constitutional injunction as to compensation. Under our practice no replication can be ■filed to a plea or answer (section 3122, Civ. Code 1907) ; but, when a plea good on its allegations is filed, matter in avoidance may, as in the case of an answer, be introduced in the bill by amendment. When this is done, the defense must meet the bill as amended, and a plea not doing so is insufficient. .The proceedings in this case, *659being prior to the adoption of the present Code, are not governed by section 3115 as it now stands, as to immaterial and insufficient pleas. We therefore must hold that the action of the lower court, in holding the pleas, 4, 5, and 7 to be sufficient, was erroneous.

The decree appealed from will be reversed, and one will be here rendered overruling the pleas.

Beversed and rendered.

Dowdell, Simpson, and Denson, JJ., concur.