50. (1) No punishment of penal diet, either singly or in combination, or of whipping, or of change of labour under section 46, clause (2), shall be executed until the prisoner to whom such punishment has been awarded has been examined by the Medical Officer, who, if he considers the prisoner fit to undergo the punishment, shall certify accordingly in the appropriate column of the punishment-book prescribed in section 12.(2) If he considers the prisoner unfit to undergo the punishment, he shall in like manner record his opinion in writing and shall state whether the prisoner is absolutely unfit for punishment of the kind awarded, or whether he considers any modification necessary.(3) In the latter case he shall state what extent of punishment he thinks the prisoner can undergo without injury to his health.