Entering the laboratory, they found themselves in a large room, quite dark, save for an electric lantern at one end that threw a brilliant circle on a sheet stretched at the other end.  The light reflected from this sheet showed the dim outlines of a tiered amphitheater before which was a long table spread with strange-looking instruments, electrical machines and special apparatus for psychological experiments.  On the walls were charts and diagrams used by the doctor in his lectures.

“Everything ready?” inquired the magistrate after an exchange of greetings with Dr. Duprat.

“Everything,” answered the latter.  “Is this the—­er—­the subject?” he glanced at the prisoner.

Hauteville nodded and the doctor beckoned to the guard.

“Please bring him over here.  That’s right—­in front of the lantern.”  Then he spoke gently to Groener:  “Now, my friend, we are not going to do anything that will cause you the slightest pain or inconvenience.  These instruments look formidable, but they are really good friends, for they help us to understand one another.  Most of the trouble in this world comes because half the people do not understand the other half.  Please turn sideways to the light.”

For some moments he studied the prisoner in silence.

“Interesting, ve-ry interesting,” murmured the doctor, his fine student’s face alight.  “Especially the lobe of this ear!  I will leave a note about it for Bertillon himself, he mustn’t miss the lobe of this ear.  Please turn a little for the back of the head.  Thanks!  Great width!  Extraordinary fullness.  Now around toward the light!  The eyes—­ah!  The brow—­excellent!  Yes, yes, I know about the hand,” he nodded to Coquenil, “but the head is even more remarkable.  I must study this head when we have time—­ve-ry remarkable.  Tell me, my friend, do you suffer from sudden shooting pains—­here, over your eyes?”

“No,” said Groener.

“No?  I should have thought you might.  Well, well!” he proceeded kindly, “we must have a talk one of these days.  Perhaps I can make some suggestions.  I see so many heads, but—­not many like yours, no, no, not many like yours.”

He paused and glanced toward an assistant who was busy with the lantern.  The assistant looked up and nodded respectfully.

“Ah, we can begin,” continued the doctor.  “We must have these off,” he pointed to the handcuffs.  “Also the coat.  Don’t be alarmed!  You will experience nothing unpleasant—­nothing.  There!  Now I want the right arm bare above the elbow.  No, no, it’s the left arm, I remember, I want the left arm bare above the elbow.”

When these directions had been carried out, Dr. Duprat pointed to a heavy wooden chair with a high back and wide arms.

“Please sit here,” he went on, “and slip your left arm into this leather sleeve.  It’s a little tight because it has a rubber lining, but you won’t mind it after a minute or two.”