You are both correct. Oxalic acid is toxic in larger quantities but the small quantity in Wini's stalk of rhubarb only stimulated and irritated the lining of the large intestine, hence the bodies' desire to get rid of it quickly.
P.S. Rhubarb wine - the home made variety - was only palatable once the oxalic acid was neutralised with precipitated chalk.
Sheila
In an earlier post to this you questioned whether this g-aunt was into self medication. !
Remember that prior to 1948 everyone was into self-medication. Doctors needed to be paid in the days before the National Health Service so, if you couldn't afford it, grannie's favourite remedy was tried.
Remember 'Jack and Jill' He went to bed to mend his head with vinegar and brown paper
Have you ever had a Kaolin poultice applied to your chest to ease lung congestion ?
Epsom salts and glycerine were very good as a poultice for drawing boils and abscesses.
Upset stomach ? Sugarallie water i.e. liquorice dissolved in water with a little sugar. Lo and behold years later they discovered that there were actually active ingredients which helped mouth and stomach ulcers
I remember the pre-NHS days and would not want to go back to them.
Russell