JOHNSON, J.

Since the enactment of the Workmen’s Compensation Act in 1929, no rule has proved more essential to its sound and orderly administration than the one which requires that an injury to be com-pensable must be shown to have resulted from an accident arising out of and in the course of the employment. Brown v. Aluminum Co., 224 N.C. 766, 32 S.E. 2d 320; Wilson v. Mooresville, 222 N.C. 283, 22 S.E. 2d 907; Neely v. Statesville, 212 N.C. 365, 193 S.E. 664; and Rewis v. Ins. Co., 226 N.C. 325, 38 S.E. 2d 97; G.S. 97-2 (f). This principle has *91 come to be known and referred to as the rule of causal relation, i.e., that injury to be compensable must spring from the employment. Plemmons v. White’s Service, Inc., 213 N.C. 148, 195 S.E. 370; Bolling v. Belk-White Co., 228 N.C. 749, 46 S.E. 2d 838. This rule of causal relation is the very sheet anchor of the Workmen’s Compensation Act. It has kept the Act within the limits of its intended scope, — -that of providing compensation benefits for industrial injuries, rather than branching out into the field of general health insurance benefits. Vause v. Equipment Co., 233 N.C. 88, 63 S.E. 2d 173; Conrad v. Foundry Co., 198 N.C. 723, 153 S.E. 266.

True, the General Assembly by amendment in 1935 (following the decision of this Court in McNeely v. Asbestos Co., 206 N.C. 568, 174 S.E. 509), extended the scope of the Act by including a specified list of twenty-five occupational diseases which are the usual and natural incidents of particular types of employment. Chapter 123, Public Laws of 1935, now codified as G.S. 97-52 and G.S. 97-53.

The amendment of 1935, however, in nowise relaxed the fundamental principle which requires proof of causal relation between injury and employment. And nonetheless, since the adoption of the amendment, may an award for an occupational disease be sanctioned unless it be shown that the disease was incident to or the result of the particular employment in which the workman was engaged. Tindall v. Furniture Co., 216 N.C. 306, 4 S.E. 2d 894; Blassingame v. Asbestos Co., 217 N.C. 223, 7 S.E. 2d 478.

Aside from statutory definitions, an occupational disease has a well-defined meaning. Before the adoption of the 1935 amendment, this Court in McNeely v. Asbestos Co., supra (206 N.C. 568, at p. 572), defined an occupational disease as follows:

“A disease contracted in the usual and ordinary course of events, which from the common experience of humanity is known to be incidental to a particular employment, is an occupational disease, . . .”

“An ‘occupational disease’ suffered by a servant or employee, if it means anything as distinguished from a disease caused or superinduced by an actionable wrong or injury, is neither more nor less than a disease which is the usual incident or result of the particular employment in which the workman is engaged, as distinguished from one which is caused or brought about by the employer’s failure in his duty to furnish him a safe place to work.”

If a disease is not a natural result of a particular employment, but is produced by some extrinsic or independent agency, it is in no real sense an occupational disease, and ordinarily may not be imputed to the occupation or employment. 58 Am. Jur., Workmen’s Compensation, Section *92 246, p. 748. See also Schneider, 'Workmen’s Compensation, Third Edition, Text Yol. 3, Sec. 502 et seq.

The record in the instant case reflects no evidence that the fatal heart attack suffered by the deceased was in fact an occupational disease or that it was produced by his employment as a fireman. And ordinarily, a heart disease is not deemed an “injury by accident arising out of and in the course of the employment” (G-.S. 97-2 (f); Neely v. Statesville, supra), nor an occupational disease. West v. Dept. of Conservation, 229 N.C. 232, 49 S.E. 2d 398. See also Industrial Commission v. Betleyoun, 31 Ohio A. 430, 166 N.E. 380.

It is significant that claimant’s principal witness, Dr. McMillan, in reply to a direct question, said he had no opinion as to whether or not the heart attack was brought on by deceased’s employment as a fireman. And the award below is unsupported by evidence showing causal relation between the fatal disease and the employment out of which it supposedly arose.

Nor does the evidence bring the case within the principle applied in Gabriel v. Newton, 227 N.C. 314, 42 S.E. 2d 96, where an unusual exertion strained and stretched the muscles of the heart and blood vessels, causing acute dilation of the heart, which was deemed a compensable injury on the theory of accident.

Here, however, the claimant insists that the award may be sustained under the 1949 amendment (Chapter 1078, Session Laws of 1949, now codified as G.S. 97-53 (26)), which designates certain, heart diseases as occupational diseases as to firemen. This amendment singles out active members of fire departments of cities, towns, and other political subdivisions of the State, and as to such firemen makes each of certain classified heart diseases an occupational disease per se, and by legislative fiat dispenses with the necessity of proving causal relation between the heart disease and the employment.

The defendant challenges the constitutional validity of the 1949 amendment on the ground that it provides in effect for a gift or gratuity from the public treasury in direct violation of Article I, Section 7, of the Constitution of North Carolina, which provides that:

“No man or set of men are entitled to exclusive or separate emoluments or privileges from the community but in consideration of public services.”

The defendant’s challenge is well taken. In reality, the statute seeks to confer upon firemen a special privilege not accorded other municipal employees, nor to employees in private industry. It places on the taxpayers a burden which the Constitution declares it was not intended for them to bear. It creates for firemen substantial financial benefits, to be paid from the public treasury under the guise of workmen’s compensation benefits, without establishing an occupational disease as the usual incident *93 or result of the particular employment. Any such payment is in direct conflict with the foregoing constitutional prohibition against separate emoluments and special privileges, and the Legislature has no power to authorize a municipal corporation to pay any such gratuity to a particular class of its employees. Our decision here is in accord with a long line of previous decisions of this Court reflecting a consistent interpretation of this constitutional limitation in striking down legislative grants of separate emoluments and special privileges. Simonton v. Lanier, 71 N.C. 498; Motley v. Warehouse Co., 122 N.C. 347, 30 S.E. 3 (petition for rehearing denied, 124 N.C. 232, 32 S.E. 555); S. v. Fowler, 193 N.C. 290, 136 S.E. 709; Plott v. Ferguson, 202 N.C. 446, 163 S.E. 688; Edgerton v. Hood, Comr. of Banks, 205 N.C. 816, 172 S.E. 481; S. v. Sasseen, 206 N.C. 644, 175 S.E. 142; Brown v. Comrs. of Richmond County, 223 N.C. 744, 28 S.E. 2d 104. See also: Cowan v. Trust Co., 211 N.C. 18, 188 S.E. 812; S. v. Warren, 211 N.C. 75, 189 S.E. 108; S. v. Harris, 216 N.C. 746, 6 S.E. 2d 854.

In Simonton v. Lanier, supra, it was contended that the charter of the Rank of Statesville, incorporated by private-local act of the Legislature, was given the special privilege to lend money at a rate of interest in excess of that allowed by general state law. There the Court held that the charter of the bank created no such special privilege. Bynum, J., ■delivering the opinion, in referring to Article I, Sections 7 and 31, of the Constitution of North Carolina, said: “The wisdom and foresight of our ancestors is nowhere more clearly shown than in providing these fundamental safeguards against partial and class legislation, the insidious and ever-working foes of free and equal government.” (71 N.C. mid. p. 503.)

S. v. Fowler, supra, involves a conflict between the provisions of a general and a public-local statute. There, under the general statute a violation of the state prohibition law was made punishable by fine and imprisonment within the discretion of the court; whereas the public-local act, applying to only five counties, restricted the punishment to a fine in certain instances. It was held that the public-local act attempted to confer upon residents of the five counties privileges or immunities not enjoyed by other residents of the State in violation of Article I, Section 7, of the State Constitution. In a well considered opinion by Adams, J., it is stated that the public-local act grants “a special exemption from punishment or an exclusive or separate privilege which is forbidden by the cited provision. ... It follows that the provision limiting the punishment for the first offense to a fine must be regarded as an arbitrary class distinction which cannot be sustained because forbidden by the fundamental law . . .” (193 N.C. at pp. 293 and 294.)

In Edgerton v. Hood, Comr. of Banks, supra, a public-local statute provided that deposit claims of certain closed banks might be sold to *94 persons indebted to such banks on tbe date of closing, and that any such purchased claim might be set off against a debt owed by the purchaser to the same closed bank. Connor, J., speaking for the Court, said: “The statute contravenes this sound and just principle, and violates both the letter and spirit of the provision, because (1) it attempts to confer an exclusive and separate privilege on one class of creditors and debtors of a closed bank, which it denies to another class, with no just or reasonable ground for the classification; . . .” (205 N.C. bot. p. 821.)

In S. v. Sasseen, supra, an ordinance of the City of Charlotte required operators of for-hire motor vehicles within the city to post policies of liability insurance written by responsible companies authorized to do business in the State of North Carolina. The ordinance was held void as class legislation, violative of Article I, Sections 7 and 31, of the State Constitution, in that it failed to provide that the security required might be furnished by solvent individual sureties as well as corporate ones. (206 N.C. 644.)

In Brown v. Comrs. of Richmond County, supra, a local recorder’s court was abolished by act of the General Assembly before expiration of the term to which the presiding judge had been elected. Thereafter a special county court was organized under general statute, with another person being appointed judge. Later an act of the Legislature directed that the county pay the judge of the abolished court his salary for the unexpired term. It was held that the statute was violative of Article I, Section 7, of the State Constitution. In a well considered opinion written by Justice Barnhill it is stated (referring to Article I, Section 7, of the Constitution) : “This constitutes a specific constitutional prohibition against gifts of public money, and the Legislature has no power to compel or even to authorize a municipal corporation to pay a gratuity to an individual to adjust a claim which the municipality is under no legal obligation to pay (citation of authorities). Nor may it lawfully authorize a municipal corporation to pay gifts or gratuities out of public funds. . . .” (223 N.C. p. 746.)

It follows that Chapter 1078, Session Laws of 1949, is repugnant to Article I, Section 7, of the Constitution of North Carolina. Therefore the statute is declared invalid and inoperative, and the award below being unsupported by the requisite proof of causal relation between the deceased’s employment and his death (Plemmons v. White’s Service, Inc., supra (213 N.C. 148), the judgment below is

Reversed.