Carroll cared little for his immediate surroundings for he knew that once he made his point and carried it to the awakened Solar System, not only would all of the past suspicion be forgotten but he would receive an even greater reward for having suffered to carry on.
Then, as the flush of newness wore away, the guards and attendants let him alone more. All of them were trained in handling the insane and they treated each new inmate with considerable suspicion until the exact nature of the patient's instability was known.
Carroll's main and only argumentative period came when he was not permitted to work as he pleased. And so long as no one mentioned the word 'alien' in any way he was silent—lost in his thoughts and his plans.
As soon as they furnished him with working space, Carroll knew that his incarceration was a godsend. For—barring the chance that one of the guards might be alien—if he could not get out they could not get in. This was security.
The one off-chance worried Carroll. It would be hard enough to segregate the few humanoid aliens from the mass of humanity. But with the aliens occupying human bodies it was impossible. Just how it was done Carroll could not say but he considered the problem and arrived at a solution from sheer deductive reasoning.
It was pathologically impossible to consider surgery—the gross transplantation of a brain. For one thing—among many—there is the matter of blood supply. Incorrect blood matching causes death in a transfusion. This is not because of the mismatch in the blood stream per se, it is because the metabolism of the entire human body is not matched to the different type of blood.
To transplant a brain would require that something be done about the blood supply—if changed to match the brain the body would die, if not the brain would die. And there was no remote possibility that any alien brain would match human blood.
It is even difficult in many cases to graft skin from one part of a human's body to another, let alone grafting skin from one to another body—and the possibility of cross-grafting across the line of demarcation between Terran species was unthinkable.
Just with common skin.
The brain?