Complex sentence: Should the hand be placed at one's side, it would be considered a challenge, with the hand placed where a gentleman would have kept his sword or pistol.this has lapsed somewhat as the number of gentlemen in the society is in decline.
Split into simpler sentences: Should the hand be placed at one's side, it would be considered a challenge, with the hand placed where a gentleman would have kept his sword or pistol. This has lapsed somewhat as the number of gentlemen in the society is in decline.