When patients other than those receiving medical aid opt for the special scheme or the private practice of hospital practitioners, the option is made in writing, as soon as the patient is admitted, by the patient himself, a member of his family or a close relative, after the person concerned has been informed of the special conditions involved in choosing one or other of these categories. The undertaking to pay the supplements to the tariff of services, which must be precisely indicated, is signed at the same time, subject, as far as the insured are concerned, to the agreements between the public health establishments and the organisations covering the costs of care.