In 1933, Carl Jung was asked by a physician to interpret the dream of a patient, without any information about him other than the following dream:

Someone beside me kept asking me something about oiling some machinery. Milk was  suggested as the best lubricant. Apparently I thought that oozy slime was preferable. Then, a pond was drained and amid the slime there were two extinct animals. One was a minute mastodon. I forget what the other one was.

Jung correctly diagnosed this patient as having an organic problem–a blockage of of the cerebro-spinal fluid, probably due to a tumor. Although few of us would recognize the source of the dreamer’s physical problem, everyone is capable of observing the dream image of a malfunctioning machine in need of lubrication.  (Reference to follow when I re-access it).