(1)    Each county, or any 2 or more counties jointly, may establish, pursuant to s. 46.17 or 46.20 a county infirmary for the treatment, care and maintenance of the aged infirm.

   (2)   In counties with a population of 750,000 or more, such institution shall be governed pursuant to s. 46.21, but in all other counties it shall be governed pursuant to ss. 46.18, 46.19, and 46.20.

   (3)   As used in ss. 49.72 to 49.726:

      (a)    An aged infirm person is a person over the age of 65 years so incapacitated mentally by the degenerative processes of old age, or so incapacitated physically, as to require continuing infirmary care.

      (b)    A county infirmary is a county institution created pursuant to sub. (1) or (2) under the general supervision and inspection of the department pursuant to ss. 46.16 and 46.17 as to adequacy of equipment and staff to treat, care for and maintain the physical and mental needs of aged infirm persons.

   (4)   The uniform accounting system established by s. 50.03 (10) shall be used by each county infirmary and shall be subject to the conditions enumerated therein.