Complex sentence: The heat began to get to Johnson, too, by round 13, but he was still the stronger and younger man in the ring and toward the end of the round, delivered a right and a right uppercut to Jeffries' head that took their toll.
Split into simpler sentences: The heat began to get to Johnson, too, by round 13, but he was still the stronger and younger man in the ring. Toward the end of that round, he delivered a right and a right uppercut to Jeffries' head that took their toll.