Thus far in the discussion of the suability of the State, according to American constitutional law, reference has been had to suits involving the recovery of money judgments or the issuance of writs of mandamus or of injunction to state officials. There now is to be considered the question whether the principles that have been laid down are sufficient to warrant suits brought by individuals to recover possession of specific pieces of property held, in their official capacities, by officials of the States or of the United States.