Upon application of a regular employee, a leave of absence without pay may be granted by an appointing authority for the entire period of disability because of sickness or injury. Such leave need not be limited to one year, but the appointing authority from time to time may require that the employee submit a certificate from the attending physician or a designated physician. [Ord. 1306 § 44, 1968; Code 1970 § 2.42.300.]