If an employee receives an injury for which compensation is payable while he is still receiving or entitled to compensation for a previous injury in the same employment, he shall not at the same time be entitled to compensation for both injuries, unless the later injury be a permanent injury such as specified in § 42-9-30 or the second paragraph of § 42-9-10, but he shall be entitled to compensation for that injury and from the time of that injury which will cover the longest period and the largest amount payable under this title.