42 CFR § 440.10 - Inpatient hospital services, other than services in an institution for mental diseases.
(a) Inpatient hospital services means services that -
(1) Are ordinarily furnished in a hospital for the care and treatment of inpatients;
(2) Are furnished under the direction of a physician or dentist; and
(3) Are furnished in an institution that -
(i) Is maintained primarily for the care and treatment of patients with disorders other than mental diseases;
(iii) Meets the requirements for participation in Medicare as a hospital; and