"You have a right to an explanation. And I can give it to you without revealing the actual process of the time transfer. You see, the mind is capable of an indefinite number of transfers. But a body can be used for only one. Before we overcame that obstacle, we made some serious mistakes." "What happened?" * * * * * "It was pretty bad during the experimental trials," said Sandane. "The pioneers, who transferred in their own bodies, were stuck irrevocably in the past. To overcome that, some transferred only mentally, which meant they had to enter unbidden into a host body of the target period. The more highly trained mind naturally had more strength--the host lost his identity. What was worse, when the visitor transferred back he sometimes entered an occupied body instead of his own. When two equally strong minds contest for one body the result is insanity. And worst of all, the former host body was left mindless--alive, but how shall I say it--?" "Like a zombie?" the old man asked. "Somebody who don't know who he is, where he is, or what time it is?" "Yea, that's a very good description. Of course, this had to be stopped." "You didn't stop it soon enough," the old man said dryly. "Must be a lot more of you fellows from elsewhen around than I figured." "I assure you we don't do it any more. We grow bodies for transfer purposes in tanks. Like this one, for example." "Well, I do declare," the old man said. "Now, that's what I call progress. According to that, when your old body wears out, you get a new one." "We haven't achieved immortality yet. The mind has its own natural span. It is true, however, that we have a greater life expectancy, and as long as a person lives he can have a body of his choice. But let's not get off the subject. The point is that I can't transfer back without a body, or I might get into one that's occupied. And I can't take this one with me. So I have to have one that is--well, if you'll forgive me being so blunt, more or less useless to its occupant." "It's the truth, Sandy, and nobody knows it better than me. But the part I don't understand is why the body you're using has to fall apart in two weeks, if you leave it here."