Any question
(a) Whether the relevant accident has resulted in permanent disablement; or
(b) Whether the extent of loss of earning capacity can be assessed provisionally or finally; or
(c) Whether the assessment of the proportion of the loss of earning capacity is provisional or final; or
(d) In the case of provisional assessment, as to the period for which such assessment shall hold good;
Shall be determined by a medical board constituted in accordance with the provisions of the regulations and any such question shall hereinafter be referred to as the "disablement question".