delivered the opinion of the Court.

On September 5, 1958 1 appellant Juan E. Soltero Pe-ralta filed a partial appeal challenging the pronouncement included in the judgment rendered by the trial court which declared as taxable income the amount of the monthly pension granted to him by the University of Puerto Rico upon retiring from his professorship for physical disability after having rendered fifteen years of service. In the brief presented the appellant argued that “it is an essential question, of a constitutional nature, that no income tax may be levied on a compensation resulting from disability, which as a matter of fact is not an income.”

As it may be noted, this appeal does not raise a substantial constitutional question (§ 14 of the Judiciary *27Act, as amended by Act No. 115 of June 26,1958, 4 L.P.R.A. (1961 Supp.), p. 210; Rule 53.2 of the Rules of Civil Procedure of 1958) on which we may exercise our jurisdiction on appeal. Fuentes v. Secretary of the Treasury, 85 P.R.R. 472 (1962). As stated in Godreau v. Godreau, 296 F.2d 326 (1961), it is not sufficient to assert an alleged constitutional question when the issue raised, once it is properly diluci-dated, merely claims that the decision below was wrong, for “mere error does not raise a constitutional question.” However, pursuant to paragraph (f) of § 14 of the Judiciary Act, as amended by Act No. 115 of June 26, 1958, supra, we shall consider the present appeal as one for review and we shall decide the issue raised on its merits.

Pursuant to the provisions of § 7 of Act No. 135 of May 7, 1942, 18 L.P.R.A. § 638, the Superior Educational Council approved an order on November 28, 19502 establishing a retirement plan for the personnel of the University of Puerto Rico. Under its provisions a person covered thereunder could retire in the following cases:

1 — Compulsory retirement — (Art. 5, section 14): — upon having reached 65 years of age, unless the service is extended by annual periods, but in no case, after having reached 70 years of age.

2 — Optional retirement — (Art. 5, section 13) — a) upon reaching 55 years of age provided he has rendered 25 years of service, and, b) upon reaching 58 years of age with 10 years of service.

3 — Deferred retirement — (Art. 6, sec. 15) : — any member less than 58 years of age who has rendered 10 years of *28service may apply for retirement to begin receiving the corresponding pension upon reaching said age.

4 — Retirement for physical or mental disability — (Art. 9, section 24) : — any person having less than 58 years of age who has rendered 15 years of service3 may apply for retirement upon proof of said mental or physical disability to continue in the discharge of his office.

An annual pension of $1,650.81 was granted to the taxpayer, who was one time Associate Professor of the Faculty of Economy of Social Sciences of the University of Puerto Rico, “for physical disability” after having rendered fifteen years of service. The Secretary of the Treasury included the payments received during the years 1951 to 1954, both inclusive, in appellant’s taxable income.

Section 15(b) (6) of the Income Tax Act of 1924, 13 L.P.R.A. § 694(b) (6), provides that the term gross income does not include “amounts received, through accident or health insurance or under workmen’s compensation Acts, as compensation for personal injuries or sickness,...” A similar provision is contained in the Act of 1954 in § 22(b) (5), 13 L.P.R.A. § 3022 (Supp.) by virtue of which an identical solution is applied for all the tax years involved in this action.4

In general terms it may be affirmed that the payments made as compensation for services already rendered constitute taxable income, Flax v. Treasurer, 76 P.R.R. 365, 368 (1954). Thus, the pension granted to an employee in consideration and recognition for a prolonged period of services rendered to the State, constitutes compensation for such services and should be included as part of the taxpayer’s income, Emmanuelli v. Secretary of the Treasury, 76 P.R.R. *29889 (1954); cf. Treasurer v. Tax Court, 70 P.R.R. 467 (1949), even though said pension has been granted under a special law, Treasurer v. Tax Court, 73 P.R.R. 830 (1952). It is of significant importance to determine, therefore, whether the pension payments received by the taxpayer correspond, among other factors, to the rendition of services for a specific period of time.

However, when the retirement pension obeys exclusively to a physical or mental disability derived from or connected with the scope of the employment, the amounts received on that account are not to be included in the gross income because they partake of the nature of workmen’s compensations. Frye v. United States, 72 F. Supp. 405 (D.C. D.C. 1947) is the leading case for the rule set forth, but as stated in the opinion rendered, the question depends ultimately on the language of the statute in question.5 See, also, *30Doogan v. United States, 154 F. Supp. 703 (Ohio 1957); Riley v. United States, 156 F. Supp. 751 (Ct. Cl. 1957); William L. Neill, 17 T.C. 1015 (1951); I.T. 3917, CB 1948-2, p. 10; I.T. 3877, CB 1947-2, p. 15; I.T. 3281, CB 1939-1, p. 97; 1 Mertens, Law of Federal Income Taxation 57, § 7.20. Where in order to obtain retirement it is necessary to have rendered services for a specific period of time — although less if it concurs with a disability — the general rule is applied and the payments received are taxable, Waller v. United States, 180 F.2d 194 (D.C. 1950); Allen v. Spencer, 214 F.2d 205 (D.C. 1954); Gerald W. McDonald, 33 T.C. 540 (1959); Marshall Sherman Scarce, 17 T.C. 830 (1951); Joseph B. Simms, 17 T.C. 1 (1951); Elmer D. Pangburn, 13 T.C. 169 (1949); Rev. Reg. 269, CB 1958-2, p. 16; I.T. 3760, CB 1945-1, p. 54; I.T. 3428, CB 1940-2, p. 60.

As may be noted, the pension granted under the retirement plan for the University personnel and designated “for physical or mental disability” requires, to be awarded, that the employee should have rendered services to the institution for at least 15 years. That is, it is not sufficient that the disability should take place while the employee is on duty, but there should also concur the requirement of services for a minimum number of years. In this sense, it is but an advanced retirement for years of service. The petitioner could have retired with only 10 years of service if he had been 58 years of age, but since he had not reached that age, he is allowed to be pensioned “for disability” after having rendered 15 years of service. In the above-cited cases in which it was held that the pension received was not to be included in the individual income tax return, the Retirement Act did not require service for a specific number of years, but only that the disability should arise in the course of the employment and as a result thereof.6

*31Furthermore, appellant likewise failed to establish that his disability was occupational. In the course of an argument in the trial court, the taxpayer stated that “I became a cripple going up and down the stairs, remaining standing for a long time, I was the victim of hemorrhages and I was about a year and a half under treatment,” but no evidence was offered to that effect. In any event, in view that services for a specific period is required in addition to the disability to continue in the employment, this fact is of no practical importance.

The respondent court did not err in deciding that the payments received by the appellant were to be included in his gross income. The writ issued will be quashed and the judgment rendered by the Superior Court, San Juan Part, on June 20, 1958, will be affirmed.