This action is founded on Gen. Sts. c. 12, § 40, which provide that the holder of a mortgage, upon taking possession of real estate thereunder, shall be liable to pay all taxes due thereon, to be recovered of him in an action of contract by the collector. This statute went into operation June 1,1860. The mortgage which the defendants hold as assignees was made in 1849, and they contend that the statute does not apply to mortgages existing before its enactment; and that if it did so, it would be void as to them, because it would have an ex post facto operation. But they took possession February 12, 1861, and as this was after the statute went into operation, its language includes them. And we do not think it is objectionable as an ex post facto law; for long before their mortgage was made, mortgaged land was subject to a lien for taxes ; and the only change which the statute makes is, that if a mortgagee enters upon land thus subject to a lien for taxes, he thereby makes himself personally liable to pay them. It merely enlarges the collector’s remedy, in case the mortgagee shall choose to do the act designated. Judgment affirmed.