Any municipal employee of any city of the first class who shall have received permanent disability in the performance of his duty, or shall be suffering from permanent injury or disease, shall, upon the certificate of a physician designated for that purpose by the pension commission, be retired on a pension equal to one-half of his salary at the time of his retirement.

Where, however, any such municipal employee shall desire to retire by reason of such injury or disease, he shall apply in writing to the pension commission for such retirement. The pension commission shall, thereupon, call to its aid a regularly licensed and practicing surgeon or physician and the applicant may also call to his aid a regularly licensed and practicing surgeon or physician. If the two surgeons or physicians so called fail to agree on the physical condition of the applicant, the pension commission may call a third and disinterested, licensed and practicing surgeon or physician. The determination of the majority of the three surgeons or physicians, who shall first be duly sworn, shall be reduced to writing and signed by them. The president of the pension commission may administer oaths to such surgeons, physicians or other persons called regarding the matter before the commission. The commission shall determine, by resolution, whether the applicant is entitled to the benefits of this article and shall consider the determination of the surgeons or physicians in reaching its decision.