This horrible phase of insanity is not, fortunately, a common one. But there are maniacs of the Ripper type still at large. There have been several crimes of the Ripper character committed in low lodging-houses during recent years, and the perpetrator has always succeeded in making his escape and in retaining his liberty.

But the bulk of the dangerous lunatics at large are not systematic assassins. They are only wrought to frenzy by a fancied grievance or the stress of circumstance.

Many of the mysterious crimes of London which are apparently motiveless are the deeds of men who are insane on the subject of persecution. The victims of this form of delusion imagine that some person, often a public character or a celebrity constantly referred to in the Press, is secretly injuring them.

The murder of a popular actor some years ago was due to this cause. A man to whom he was an utter stranger imagined that the actor was keeping him out of an engagement, and he assassinated his imaginary enemy at the stage door of a West End theatre.

If a list could be prepared of the people against whom some lunatic at large has sworn to be revenged for a grievance which exists solely in the imagination of the aggressor, it would be a very alarming document.

It would show the world that a large number of men and women who are dangerously insane are living unrestrained lives, mixing with their fellow-citizens without let or hindrance, and only waiting for the opportunity to attack a supposed enemy.

Many of these people are looked upon by their acquaintances merely as cranks. After the Beck case I received hundreds of letters from people with a grievance; a large number of them were well written, and the addresses at the head of them showed that the writers were in a good position.

In some of these letters there was a threat of what would happen if the "persecutor" was not compelled by the Press to abandon his course of conduct. Some of them contained an unmistakable hint that murder might be the result if the persecution were not stopped or the wrong redressed.

And all these people, absolutely insane, were free from any sort of guardianship or control. Three of them called upon me.

One came late at night. He rushed in directly the door was opened and walked into my study, the door of which was open, before the astonished servant could interfere.