Most of the students had left the theatre, and the remainder had gathered round the lecturer's table to listen to the informal comments that Dr.Thorndyke was wont to deliver on these occasions in an easy, conversational manner, leaning against the edge of the table and apparently addressing his remarks to a stick of blackboard chalk that he held in his fingers.
"The problem of survivorship," he was saying, in reply to a question put by one of the students, "ordinarily occurs in cases where the bodies of the parties are producible, or where, at any rate, the occurrence of death and its approximate time are actually known.

But an analogous difficulty may arise in a case where the body of one of the parties is not forthcoming, and the fact of death may have to be assumed on collateral evidence.
"Here, of course, the vital question to be settled is, what is the latest instant at which it is certain that this person was alive?
And the settlement of that question may turn on some circumstance of the most trivial and insignificant kind.

There is a case in this morning's paper which illustrates this.

A gentleman has disappeared rather mysteriously.

He was last seen by the servant of a relative at whose house he had called.