What does David finally do, in response to Alan's sarcasm and name-calling?

Finally, after being called Whig and feeling as if he was about to die, David exploded with anger. He criticized Alan, espousing that Alan should pay respect to the Whigs and Campbells who continually beat him. Alan was offended but David continued, finally pulling his sword and challenging Alan. Alan revealed his sword but then threw it upon the ground, collapsing into sadness. David's anger finally left him but he could not take back what he had said. He appealed to Alan with his seriously ill health. Alan ran to his side, apologized graciously, and offered to carry him though David was much larger in size.