It brings back images of experiments with twitching frogs' legs and that famous weekend when Shelley, Byron, Mary Godwin and Doctor Galivari(?) were banged up during that thunderstorm, when everyone wrote a short horror story except Mary who wrote Frankenstein.

That's the point. At that time 'mainstream' western science thought it inevitable that the life force would one day be isolated & examined under a microscope, thus confounding the centuries of mumbo-jumbo which had accumulated around the concept.

I don't think it's any coincidence that Rhadasaomi appeared at roughly the same time, or that they went down the 'science of the soul' road, which of course turned out to be a dead end.

So what would your own idea of the life force be?

I don't have one. Birth & Death remain as mysterious now, from the why pov, as ever they have done.