The old hypothesis of the influence of a magnet on the human body was at this time revived, and Charcot’s pupils found that when a susceptible female patient held in the hand a bar of iron surrounded by a coil of copper wire leading to a chemical electric cell or battery nothing happened so long as the connection was broken. But as soon as the wire was connected so as to set up an electric current and to make the bar of iron into a magnet, the hand and arm (up to the shoulder) of the young woman holding the bar, lost all sensation. She was not allowed to see her hand and arm, and was apparently quite unconscious of the thrusting of large carpet-needles into, and even through, them, though as long as the bar of iron was not magnetised she shrunk from a pin-prick applied to the same part. I saw this experiment with Charcot and some others present, and I noticed that the order to an assistant to “make contact,” that is to say, to convert the bar of iron into a magnet, was given very emphatically by Charcot, and that there was an attitude of expectation on the part of all present--which was followed by the demonstration by means of needle-pricking that the young woman’s arm had lost sensation, or, as they say, “was in a state of anæsthesia.” Charcot went away saying he should repeat the experiment before some medical friends in an hour or two. In the meantime, being left alone in the laboratory with my companion as witness, I emptied the chemical fluid (potassium bichromate) from the electric battery and substituted pure water. It was now incapable of setting up an electric current and converting the bar into a magnet. When Charcot returned with his visitors, the patient was brought in, and the whole ritual repeated. There was no effect on sensation when the bar was held in the hand so long as the order to set the current going, and so magnetise the bar, had not been given. At last the word was given, “Make!” and at once the patient’s arm became anæsthetised, as earlier in the day. We ran large carpet-needles into the hand without the smallest evidence of the patient’s knowledge. The order was given to break the current (that is, to cease magnetising the bar), and at once the young woman exhibited signs of discomfort, and remonstrated with Charcot for allowing such big needles to be thrust into her hand when she was devoid of sensation! My experiment had succeeded perfectly.