Clever, isn't it? This 1907 design from White-Merrill was made for horse cavalry soldiers who needed a one-handed weapon:
The unusual feature of this pistol was the provision of a finger-operated lever beneath the trigger guard, which, when squeezed, drew back the slide to allow the weapon to be cocked with one hand. This feature is said to have been provided for the benefit of the US Cavalry, who could thus retain control of their horse while cocking the pistol.
It could fire ten .45-caliber rounds fed individually or with a stripper clip.