Opinion by
Mr. Justice Potter,This is an appeal from a judgment awarding a writ of *149mandamus, commanding the auditor general to draw his warrant upon the state treasurer for the sum of ten hundred and thirty-five dollars in favor of the National Limestone Company, as specified in the requisition of the state highway commissioner, and commanding the state treasurer upon presentation of said warrant, to pay the same, and charge the amount against the fund received from registration and license fees for automobiles under the Act of July 7,1913, P. L. 672. The first question raised is whether the attorney general is the proper person to act as relator in these proceedings. It is contended that this writ should not have issued at the relation of the attorney general, but at the relation of the state highway commissioner. It is provided in the Mandamus Act of June 8, 1893, P. L. 346, Sec. 4, that, “When the writ is sought to procure the enforcement of a public duty, the proceeding shall be prosecuted in the name of the Commonwealth, on the relation of the attorney general......Provided, further, that when said proceeding is sought to enforce a duty affecting a particular public interest of the State, it shall be on the relation of the officer entrusted with the management of such interest.” The distinction intended to be made between a public duty, and a duty affecting a particular public interest of the State is not very clear. The former term is broad enough to include the latter. While it may be said that the duty sought to be enforced in the present case, is one affecting a particular public interest of the State, that is, the maintenance of its system of highways, yet at the same time the duty sought to be enforced is no less a public one. It is to be discharged by the auditor general and state treasurer, two public officers, acting in their official capacity. It is a duty defined by a public statute, to be discharged in compliance with the requisition of the state highway commissioner, another public officer, acting under authority of the same statute. Under the tenth section of the statute the money derived from the registration of motor vehicles and from licenses *150issued to their drivers is to be devoted to the purpose of assisting in the construction, maintenance and repair of state highways upon which the motor vehicles thus regulated are to operate. The system of highways, to which that section of the statute refers is not something local or special, but is a matter of general concern: State Highway Commissioner v. Chambersburg & Bedford Turnpike Co., 242 Pa. 171. The question here, is as to which one of two public officers is to prosecute the proceeding. The requirement that when the duty sought to be enforced affects a particular public interest, it shall be on the relation of the officer in charge of such interest, is no more mandatory than the language of the preceding proviso, which states that in certain cases, the proceeding shall be on the relation of the district attorney of the proper county. Yet in the case of Stegmaier v. Jones, 203 Pa. 47, it was held, that this proviso does not prevent the attorney general from acting in cases where it would be proper for the district attorney to act, but that either officer may act. We can see no good reason why in this case, any inconsistency between the language of the section, and of the proviso under consideration, should not be removed as suggested by counsel for appellee by reading the word “shall” as “may.” The principle which justifies this construction is familiar. It is stated in 2 Sutherland on Stat. Consr. (2d Ed., 1904), Sec. 640, p. 1155, where it is said: “The word ‘shall’ in its ordinary sense is imperative...... But the intent of the act controls, and when the spirit and purpose of the act require the word ‘shall’ to be construed as permissive it will be done.” In 35 Cyc. L. & Pr. 152, it is said: “It (shall) may be construed to mean ‘may’ when no right or benefit to any one depends on its imperative use; when no advantage is lost, when no right is destroyed, when no benefit is sacrificed, either to the public or to any individual, by giving it that construction, or when it is absolutely necessary to prevent irreparable mischief, or to construe a direction so that it *151shall not interfere with vested rights, or conflict with the proper exercise of power by either of the fundamental branches of government; and it also means ‘may’ when used by a legislature in a grant of authority to a court.” In Bladen v. Philadelphia, 60 Pa. 464, Mr. Justice Shabswood said (p. 466): “It would not perhaps be easy to lay down any general rule as to when the provisions of a statute are merely directory, and when mandatory or imperative. Where the words are affirmative, and relate to the manner in which power or jurisdiction vested in a public officer or body is to be exercised, and not to the limits of the power or jurisdiction itself, they may and often have been construed to be directory.” In the present case we think that the provision that a proceeding to enforce a duty affecting a particular public interest, shall be on the relation of the officer in charge of that interest, may well be regarded as directory in character, and that either such officer, or the attorney general under his direct authority to enforce the performance of a public duty may act as relator. The provision does not relate to the substance of any duty to be performed, but it merely designates an officer who is to act. The important thing, is the enforcement of a duty affecting the public interest. Whether it be the hand of one officer or another that sets the machinery of the law in motion for that purpose, is of no great moment. We see no reason to differ with the conclusion reached by the court below, that this suit was properly brought on the relation of the attorney general.
That the auditor general and the state treasurer were under the circumstances properly joined as defendants cannot be seriously questioned. The purpose is to compel the performance of an official duty which requires successive but interdependent action by the two officers. Unless they are joined, the relator will’have no effective writ. The principle which authorizes such joinder is thoroughly justified, and well illustrated in Labette County Commissioners v. United States, 112. U. S. 217, *152and in Com. ex rel. Green v. Gregg, 161 Pa. 582; Chelten Trust Co. v. Blankenburg, 241 Pa. 394; Cunningham v. Dunlap, 242 Pa. 341.
The reason given by the state treasurer for his refusal in this case to pay a warrant based upon the requisition of the state highway commissioner, was his belief that the 10th section of the Act of July 7, 1913, P. L. 672, is unconstitutional. It is contended on his behalf that this particular section of the act is in violation of sections 3 and 15, of Art. Ill, of the Constitution. The first of these reads as follows: “No bill, except general appropriation bills, shall be passed containing more than one subject, which shall be clearly expressed in its title.” Section 15 is in this language: “The general appropriation bill shall embrace nothing but appropriations for the ordinary expenses of the executive, legislative and judicial departments of the Commonwealth, interest on the public debt, and for the public schools; all other appropriations shall be made by separate bills, each embracing but one subject.” Does the act under consideration contain more than one subject, and if but one, is that subject clearly expressed in the title? The general subject of the act is the regulation of motor vehicles, and that subject is clearly expressed in the title. Of the twenty-four sections of the statute, the only one that is questioned as not being sufficiently indicated in the title, is the tenth, and that provides for the disposition of the fund derived from registration fees, and from license fees imposed by the act in question. The suggestion that provisions in the statute for granting licenses, and for disposing of the money received from the grant, are not germane to each other, seems to us to be without force. Having as part of the system of regulating the operation of motor vehicles on the state highways, provided for the imposition of registration and license fees, nothing would follow more naturally than a direction as to what disposition should be made of those fees. In this instance, the legislature directed that *153after the collection by the state highway department, the fees should be paid into the state treasury for safe keeping, and should be placed in a separate fund, to be available for the use of the State Highway Department, upon requisition of the state highway commissioner. The general subject dealt with by the act is the regulation of motor vehicles, in their operation upon the public highway. As an essential element in this regulation, registration and the payment of license fees were required. Clearly the disposition of such fees, paid as an incident to the system of regulation, was a matter closely allied thereto, and naturally to be considered by the legislature in connection with the main purpose of the act. The statute would have been incomplete, had it required the payment of fees, without providing for any disposition of them. No argument should be required to show that provisions for attaining various objects, which relate to the general subject of the bill, may be dealt with by its terms, without laying it open to the charge of containing more than one subject. A law may relate to but one subject, the liquor traffic for instance, which it may regulate in various ways, and thereby accomplish several objects. In the present case the law relates to motor vehicles, and it regulates them in a number of particulars, with the result, that a number of objects are incidentally accomplished, one of which is the creation of a fund to assist in the construction and repair of the highways, upon which the motors are operated. This particular object falls within the approved limits, as defined in our cases, such as Reber’s Petition, 235 Pa. 622; Booth & Flinn, Ltd., v. Miller, 237 Pa. 297. In the latter case, an act of assembly made an appropriation of money to a hospital, and contained provisions requiring as a prerequisite to payment, the investment of a much larger sum by the hospital, and the execution of an obligation agreeing that in case of nonuser, or use for private purposes the amount of the appropriation should be refunded. And a further pro*154vision that the amount of the appropriation should be made a lien on the premises. Yet all these objects were held to be germane to the one general subject of the legislation. We see no room for distinction in principle between that case and the present one, in so far as the matter of the law containing more than one subject is concerned. Nor is there any merit in the suggestion that the title is defective. In the title the words “providing for the disposition of fees collected” certainly give reasonable notice of the disposing clause of section ten, and invite examination thereof by any one interested. It is further suggested that the act offends against section fifteen of the Constitution which provides that “all other appropriations shall be made by separate bills, each embracing but one subject.” There are two answers to this contention, each equally persuasive and both conclusive of the question involved. The first is that the Act of 1913 was a separate bill when it was considered by the legislature and it contains only one subject within the meaning of the organic law as we have already pointed out in this opinion; the second is that this provision of the Constitution was only intended to apply to the biennial appropriations made by the legislature out of the general revenues of the Commonwealth. It has no application to a fund created for a special purpose and dedicated by the act under which such fund is to be created to a particular use. The appropriation of the fund so created continues as long as the act which dedicates it to a particular use remains in force.
Counsel for, appellants also contend that section ten infringes uponi the constitutional functions of the auditor general and state treasurer. The answer to this is, that while these officers are named in the Constitution, yet their duties are not therein defined. That was left to the legislature. That body did define the duties of these officers, prior to the present Constitution, in the Act of March 30,1811, 5 Sm. L. 228, and it is suggested that in adopting the present Constitution the continuance of *155those duties was contemplated. It must be admitted, however, that as the legislature originally prescribed those duties, it has power to alter them, and an act making such alteration cannot for that reason be held to be unconstitutional. Aside from that, we do not see that the effect of the section in question is, to take away from the auditor general or state treasurer any power that either of them possessed. It merely provides that a certain fund, over which these officers had no previous control, shall be paid into the state treasury “for safe keeping,” and kept there as a separate fund. It also prescribes the manner in which it is to be withdrawn from the treasury. It is suggested that in the appropriation the specific amount of money should have been named. This criticism is directly answered by the decision in Com. v. Barker, 211 Pa. 610, where a municipal ordinance, appropriated a certain fund not yet received and uncertain in amount. Mr. Chief Justice Mitchell there said (p. 613): “All the essentials of a valid appropriation are here, and in the absence of a constitutional or legislative restriction as to form the city councils may put their mandate in any form they choose. All that is necessary is that the language should clearly express their intent to make an appropriation: Com. ex rel. v. Gregg, 161 Pa. 582.” In the case at bar, the act fixes the maximum, beyond which the payments cannot go, that being the total amount of the moneys paid into the state treasury under its provisions. The auditor general is expressly forbidden to draw his warrant in paymeht of any requisition which exceeds the amount in the “separate fund” at the time it is made. The statute does not provide that the money derived from registration and license fees shall be paid into the state treasury generally, so as to become part of the general revenues of the Commonwealth. The state treasury is merely made a depository for such fees. They are to be paid into it “for safe keeping” and are to be “placed in a separate fund” available for the use of the State Highway Depart*156ment. The act then expressly appropriates or dedicates the fund to be thus created to the construction, maintenance, improvement and repair of the highways. That the legislature has the power, in the absence of any constitutional limitation to the contrary, to provide for the creation of a special fund for a particular use and to dedicate the fund so created to the use intended, will not be seriously controverted by any one familiar with the subject. Our Constitution contains no provision limiting the power of the legislature in this respect, and indeed such power has been exercised without challenge many times both before and since the adoption of our present Constitution. When a fund is thus created and dedicated to a particular use by an act of assembly, which provides for its safe keeping and prescribes how it shall be made available, no further legislation is needed to make the act effective. Whether it be called an appropriation, or a dedication of a particular fund, makes no essential difference, because the fund being set apart for the specified use must be so held and paid out in the manner prescribed as long as the act which provides for its creation remains in force. The requirements of Section 16, Art. Ill, of the Constitution, that “no money shall be paid out of the treasury, except upon appropriations made by law, and on warrant drawn by the proper officer in pursuance thereof,” simply means that the public funds are not to be expended in any way except as directed by the law-making power. In so far as the present case is concerned, there is no occasion to consider whether the Act of 1913, under which automobile license fees are paid, deprives the auditor general and state treasurer of any of their functions under the Act of March 30, 1811, 5 Sm. L. 228. The bill involved in this litigation was presented to the auditor general for his approval accompanied by a requisition for the amount of the same. This gave the auditor general the right to examine the bill before approving the same and drawing his warrant for the amount. Clearly,, it was *157within his province to say whether the expenditure was made in accordance with the provisions of law, and to call for such information as he could reasonably require to satisfy his mind that the debt was lawfully created before drawing his warrant in favor of the claimant. He was given this opportunity but declined to act, upon the ground that the tenth section of the Act of 1913 was unconstitutional. He was mistaken in this position as appears from what has been hereinbefore stated. He did not refuse to draw his warrant because the expenditure had not been properly made, or because the State Highway Department did not have power to make the contract, or for the reason that the amount demanded was in excess of the contract price, or that any collusion was shown in the awarding of the contract, or because the bill was not meritorious. He simply stood upon the ground that the Act of 1913 was unconstitutional and that there was no lawful authority to warrant the payment. Under such circumstances it has been frequently held that mandamus will lie. to compel the accounting officers of the Commonwealth to perform their duty, and this remedy is just as applicable to compel the performance of a duty under the Act of 1811, as under the Act of 1913, or any other statute. No officer can arbitrarily refuse to perform a duty no matter by what law that duty may be imposed. The Act of 1913 requires the auditor general upon the requisition of the state highway commissioner to draw his warrant upon vthe state treasurer for the amount specified in the requisition, but in the exercise of this power there is necessarily implied the right to make inquiry, and if necessary, to call witnesses for the purpose of obtaining such information relating to the expenditures as to justify the drawing of the warrant. But such information must relate to the merits of the bill presented for payment and to the question whether the law authorizes such expenditures. The legislature did not intend that the accounting officers should have supervision of the state *158highways, or it would not have provided for the appointment of a state highway commissioner with ample power to construct, maintain and repair these highways.
The assignments of error are overruled, and the judgment is affirmed.