I know the seeds are the most poisonous part of the plant,
but the stems/leaves (and presumably roots) are as well.

Is "Castor Oil" made from that plant, as the name implies?

I ask, because during WW I, many aircraft engines, "rotary engines,"
were lubricated with Castor Oil, which was pumped overboard rather
than recirculated. Pilots could not avoid ingesting the stuff.

In their memoirs, many wrote of the problems caused by the laxative
properties of the oil, but none of them seem to have been poisoned by
it.

Can anyone explain this?

Thanks. vince norris