By today's standards a 32 ACP is rather anemic but in the heyday of mouse guns it was rather effective at changing hostile minds. This was not due to any tremendous shock delivered to the target or any bullet driven deep into vital areas but, instead, to the medical abilities (more like inabilities) of the times. It wasn't surgical practices so much as the ability to prevent or defeat infection that became the game changer. People of the time were not nearly as afraid about getting hurt as they were of developing an infection their body could not handle. A fair number of people knew of someone who had died of infection and those who didn't were aware of the slow, painful process in which one succumbed to infection. That later infliction was as much of a stopping power as the immediate chance of death.
The prime time of this class of cartridge ran up to WWII when the ability to fight infections became common and widespread. Before 1930, infection was a serious concern as there was little other than home remedies to fight it. Penicillin, sulfa drugs, and tetanus shots became available in the 30s and were widespread after WWII. As the dangers of infection lessened, the effectiveness of this class of cartridge faded. Add in the advances in surgical procedures and abilities and the mouse guns with their related cartridges became even less of a threat. I still wouldn't want to shot with one but I'd rather chance a wound with them to one from something larger.
