"I think the best name for it is a tumor," he said slowly. "I told them in there it was a tumor. I wish I knew myself." "A tumor! I don't understand!" "I don't either, Pat--not fully. It's something on or beyond the border of medical knowledge. I don't think any living authority could classify it definitely." "But tell me!" she cried fiercely. "Tell me!" "Well, Honey--I'll try." He paused thoughtfully. "Cancers and tumors--sarcomas--are curious things, Dear. Doctors aren't at all sure just what they are. And one of their peculiarities is that they sometimes seem to be trying to develop into separate entities, trying to become human by feeding like parasites on their hosts. Do you understand?" "No," said the girl. "I'm sorry, Dr. Carl, but I don't." "I mean," he continued, "that sometimes these growths seem to be trying to develop into--into organisms. I've seen them, for instance--every surgeon has--with bones developing. I've seen one with a rather perfect jaw-bone, and little teeth, and hair. As if," he added, "it were making a sort of attempt to become human, in a primitive, disorganized fashion. Now do you see what I mean?" "Yes," said the girl, with a violent shudder. "Dr. Carl, that's horrible!" "Life sometimes is," he agreed. "Well," he continued slowly, "I opened up our patient's skull at the point where the fluoroscope indicated the bullet. I trephined it, and there, pierced by the shot, was this--" He hesitated, "--this tumor." "Did you--remove it?" "Of course. But it wasn't a natural sort of brain tumor, Honey. It was a little cerebrum, apparently joined to a Y-shaped branch of the spinal cord. A little brain, Pat--no larger than your small fist, but deeply convoluted, and with the pre-Rolandic area highly developed." "What's pre-Rolandic, Dr. Carl?" asked Pat, shivering. "The seat of the motor nerves. The home, you might say, of the will. This brain was practically all will--and I wonder," he said musingly, "if that explains the ungodly, evil fascination the creature could command. A brain that was nothing but pure will-power, relieved by its parasitic nature of all the distractions of a directing body! I wonder--" He fell silent. "Tell me the rest!" she said frantically. "That's all, Honey. I removed it, and I guess I'm the only surgeon in the world who ever removed a brain from a human skull without killing the patient! Luckily, he had two of them!" "Oh God!" murmured the girl faintly. She turned to Horker. "But he will live?" "I think so. Your shot killed the devil, it seems." He frowned. "I said it was a tumor; I told them it was a tumor, but I'm not sure. Perhaps, just as some people are born with six fingers or toes on each member, he was born with two brains. It's possible; one developed normally, humanly, and the other--into that creature we faced last night. I don't know!"