It was a difficult job. His chemical senses operated essentially on large molecules such as proteins and polysaccharides; he could identify and distinguish these by means most nearly analogous to the human sense of touch. It was intuitively obvious to him why many of them behaved as they did in a human organism-or any other living thing-just as a simple gear train is obvious in its operation to most human beings. However, if the same human being, who had no training in complex mechanics, were suddenly to be con fronted with the maintenance of a twenty-eight cylinder "corncob" airplane engine, he would be in somewhat the Hunter's situation faced with the up keep of a living body from a planet his people had not visited before.

The salt problem looked simpler, but actually branched out into another field. It was a little like asking a mechanic who had been trained on the air plane engine to work on a television set. The sodium and chloride ions, as well as the magnesium and other chemical species in sea water, were very different from proteins-far smaller, and too uniformly charged to offer a handle to most of the alien's sensing and manipulating powers. He knew that all living cells had selective permeability to such things by nature of their chemical architecture. He knew some of the ways in which this was done, but by no means all of them; even to him, a cell was a very complex structure. On a scale which represents a water molecule by a fairly large pea, a human red blood cell is over half a mile across, and has much detail to be learned by anyone proposing to repair or alter its structure-or even imitate it.

There were many members of the Hunter's species to whom the construction of an effective desalting gland would have been a trivial matter, but the highly experienced detective was not among them.

He tried, butt asking Maeta occasionally how she felt was superfluous. He knew that he was getting very little deionized water through her skin.

Bob kept feeding them, and of course a certain amount of waterwas available from the oxidized foods, but it was not enough to keep the girl comfort able. The Hunter could, and did, block the nerves which would have been transmitting excruciating pain from her injuries, but the thirst sensation was far more subtle in origin, and he could do nothing about it.

Maeta did not complain, but sometimes she could not help saying something which showed how she felt. She never blamed the Hunter or anyone else, except once to comment on her own poor judgment in putting to sea when she had. But to the detective the whole situation was obviously his own fault. His feelings of guilt never wavered. He wished she would not talk at all, but could not bring himself to ask her not to.

It was fortunate that he did not. It was one of her remarks which dropped the most important piece of the jigsaw puzzle into place for him. The remark was painful to him, painful enough so that he could not resist arguing, in fact, but it proved useful.

"I'm afraid I felt better the other time I fought thirst this way, Hunter," she said. "I suppose it isn't working so well this time because I've been hurt so. You're sure I won't die of thirst this time?"

"Unless it takes two or three days for us to be found," the symbiont assured her, "you're in no real danger. With enough food, I could get the water to keep you alive indefinitely, though perhaps not very comfortably. I'm getting a little into you from the sea, too-more than would come through your skin with out help, in spite of what you were saying."

"That's hard to believe," she said slowly and drowsily. "The other time I didn't get thirsty at all. I re member." The Hunter was slightly irritated by his failure at what the human beings considered a simple job. His answer showed this slightly.

"It may have been your additional reserves, Maeta, but I suspect it's just ordinary human good-old-times reaction," he said. "There is just no way that significant amounts of water-even sea water-could get through your skin, which is effectively designed to keep water inside your system. If any did get in, it wouldn't help your thirst at all.”

"It did. I remember. Twice."

"But you weren't hurt, and you were only a few hours without water, and you knew it was coming soon. You've never been in a situation like this, I'm sure."

"I wasn't hurt, no, and the first time, you're right-it was only five or six hours and I'd emptied my can teen without thinking how long I was going to be there. I was a little careless in those days. The second time I'd accidentally spilled my bucket during the first hour, and I'd done a lot of work and was really thirsty before I noticed it had tipped. The boat didn't come back to pick me up until way after dark. It was a very long day. And I soaked in the lagoon. And I didn't get thirsty."

A thought crossed the Hunter's mind, startling enough to silence him for several seconds while he tried to work out its implications.

Finally he asked, "How long ago was all this? The last two or three years, or back when you were very young?"

Maeta answered with no hesitation. "Not very long ago. Both times, I was collecting for the Museum Ex change-that's the group that arranges trades of specimens between exhibitors and collectors all over the world-and I didn't start working with them until after I started at the library, of course. I didn't know about them until then." "Less than three years, then."

"About that," she agreed.

The Hunter decided not to ask for details about the carelessness she had been showing at about that time. She was a very alert young woman, he had come to realize^ and lie did not want her thinking, just yet, along the lines which had just occurred to him. He was not sure enough yet; one didn't jump to conclusions, at least not out loud.

Also, he didn't know whether to be annoyed at the waste of the time spent on looking for spaceships, or to be relieved that there would be no need to deliver anymore messages to the one with the booby trap.

14. Professional

The amphibian settled onto Eight's lagoon about an hour before sunset, and taxied close to the beach where the castaways were waiting. A rubber dinghy emerged from the waist hatch, followed by Dr. Seever. He paddled ashore without waiting for anyone to accompany him, and looked over the three standing and lying at thewater's edge. He whistled gently as he saw Maeta.

"Ladies first, it looks like," he remarked as he stepped out of the dinghy and pulled it ashore. He started to bend down for a closer examination, and was visibly startled at the cheerful way the girl spoke.

"I'm reasonably all right, Doctor," she said. The Hunter is with me, and all I need is a gallon or so of water. Better check up on Bob; he got some cuts when we landed."

"I'll last," Bob forestalled questioning. "I was getting feverish two or three hours ago, and Mae noticed it. She told the Hunter to come over and clean me out. I objected, but you don't argue with her, as you may have noticed. She had the Hunter on her side, any way. He took care of the bugs and went back to her, so I'm all right for a while."

"And how about me?" asked Andre".

"A broken shoulder, I think," Bob said to the doc tor. "He may look the best, if you don't count that bruise, but he probably does need you the most."

Seever sighed. "Hunter, if your people really decide to make close contact with humanity, medical practice is certainly going to change a lot. I suppose I should be grateful that it won't disappear entirely, though maybe I wouldn't mind retiring early at that. Come on, all of you. I'll work on you in the plane, Andy; I gather you've joined the group."

"Well," said Bob, "we have to do something to keep him from sticking skewers through people just to see if they can live through it. Maybe you should train him as a surgical assistant, Doc."