N.Y. Second Class Cities Law § 170

§ 170. Commissioner; deputy. The commissioner of public welfare may\nappoint one or more deputies, and such other subordinates as may be\nprescribed by the board of estimate and apportionment. In case of the\nabsence or disability of the commissioner or of a vacancy in the office,\na deputy shall discharge the duties of the office until the commissioner\nreturns, his disability ceases or the vacancy is filled. The\ncommissioner, and the deputies before entering upon the discharge of the\nduties of their respective offices, shall each execute and file with the\ncity clerk an official undertaking in such penal sum as may be\nprescribed by the common council.\n