“Of course a severed organ like that,” he said, “will run down quicker than if it had the co-operation of the others, and presently I shall apply a gentle electric stimulus to it. If I can keep that glass bowl under which it beats at the temperature of a frog’s body, in sterilised air, I don’t see why it should not go on living. Food--of course there’s the question of feeding it. Do you see what that opens up in the way of surgery? Imagine a shop with glass cases containing healthy organs taken from the dead. Say a man dies of pneumonia. He should, as soon as ever the breath is out of his body, be dissected, and though they would, of course, destroy his lungs, as they will be full of pneumococci, his liver and digestive organs are probably healthy. Take them out, keep them in a sterilised atmosphere with the temperature at 98·4, and sell the liver, let us say, to another poor devil who has cancer there. Fit him with a new healthy liver, eh?” “And insert the brain of someone who has died of heart disease into the skull of a congenital idiot?” I asked. “Yes, perhaps; but the brain’s tiresomely complicated in its connections and the joining up of the nerves, you know. Surgery will have to learn a lot before it fits new brains in. And the brain has got such a lot of functions. All thinking, all inventing seem to belong to it, though, as you have seen, the heart can get on quite well without it. But there are other functions of the brain I want to study first. I’ve been trying some experiments already.” He made some little readjustment to the flame of the spirit lamp which kept at the right temperature the water that surrounded the sterilised receptacle in which the frog’s heart was beating. “Start with the more simple and mechanical uses of the brain,” he said. “Primarily it is a sort of record office, a diary. Say that I rap your knuckles with that ruler. What happens? The nerves there send a message to the brain, of course, saying--how can I put it most simply--saying, ‘Somebody is hurting me.’ And the eye sends another, saying ‘I perceive a ruler hitting my knuckles,’ and the ear sends another, saying ‘I hear the rap of it.’ But leaving all that alone, what else happens? Why, the brain records it. It makes a note of your knuckles having been hit.” He had been moving about the room as he spoke, taking off his coat and waistcoat and putting on in their place a thin black dressing-gown, and by now he was seated in his favourite attitude cross-legged on the hearthrug, looking like some magician or perhaps the afrit which a magician of black arts had caused to appear. He was thinking intently now, passing through his fingers his string of amber beads, and talking more to himself than to me.