N.Y.C. Charter § 564: Section 564. Suits and service of papers.

The department may sue and be sued in and by the proper name of "Department of Health and Mental Hygiene of the City of New York", and service of all process in suits and proceedings against or affecting the department, or other papers, may be made upon the commissioner or official designated by him, and not otherwise; except that, according to usual practice in other suits, papers in suits to which the department is a party may be served on the corporation counsel or such assistant as may be assigned by him to the department.