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.