In chancery the defendant, instead of filing a formal demurrer or plea, may insist on any special matter in his answer, and have the same benefit therefrom as if he had pleaded the same or demurred to the bill. Rule 10. The answer may be amended by inserting the demurrer in it. The probate of the will raised the issue of fraud alleged in the bill. There is no allegation of insufficiency of notice or other reason why the probate court, in *367 appointing tbe guardian and allowing the will, did not have jurisdiction. A decree of the probate court upon matters within its jurisdiction cannot be impeached by a collateral proceeding. Gordon v. Gordon, 55 N. H. 399; Lyme v. Allen, 51 N. H. 242; Railroad v. Railroad, 57 N. H. 200; Poplin v. Hawke, 8 N. H. 124. When the answer is withdrawn, or amended by making the demurrer a part of it, the demurrer will be sustained.

Case discharged.