Any employee of the water department who shall have received permanent disability in the performance of his duty, shall, upon certificate of the surgeon or 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, a person desires to retire by reason of injury or disease, he shall apply in writing to the pension commission for retirement. Thereupon the pension commission shall call to its aid a surgeon or physician who shall represent the commission and the applicant may call to his aid a regularly licensed and practicing physician or surgeon. If these two physicians or surgeons fail to agree upon the physical condition of the applicant, the pension commission may call a third disinterested licensed and practicing physician or surgeon and the determination of the majority of such three physicians, they being first duly sworn in the case, shall be reduced to writing and signed by them. The president of the pension commission may administer an oath to such physicians or surgeons or any other person 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 physicians’ or surgeons’ determination in arriving at its decision.