The right of private defence of the body extends, under the restrictions specified in section 37, to the voluntary causing of death or of any other harm to the assailant, if the offence which occasions the exercise of the right be of any of the descriptions hereinafter enumerated, namely:—
(a) such an assault as may reasonably cause the apprehension that death will otherwise be the consequence of such assault;
(b) such an assault as may reasonably cause the apprehension that grievous hurt will otherwise be the consequence of such assault;