is Dr. Lett. He was the greatest of our physicians. Now he is nearly the last."

"Agreed," said the bland man, as zestfully as before. "But now the Interstellar Medical Service sends someone before whom I should bow! Someone whose knowledge and experience and training is so infinitely greater than mine that I become abashed! I am timid! I am hesitant to offer an opinion before a Med Service man!"

It was not unprecedented for an eminent doctor to resent the implied existence of greater skill or knowledge than his own. But this man was not only resentful. He was derisive.

"I came here," said Calhoun politely, "on what I expected to be a strictly routine visit. But I'm told there's a very grave public health situation here. I'd like to offer any help I can give."

"Grave!" Dr. Lett laughed scornfully. "It is hopeless for poor planetary doctors like myself! But not, of course, for a Med Ship man!"

Calhoun shook his head. This man would not be easy to deal with. Tact was called for. But the situation was appalling.

"I have a question," said Calhoun ruefully. "I'm told that paras are madmen, and there's been mention of suspicion and secretiveness which suggests schizo-paranoia and—so I have guessed—the term para for those affected in this way."

"It is not any form of paranoia," said the planetary doctor, contemptuously. "Paranoia involves suspicion of everyone. Paras despise and suspect only normals. Paranoia involves a sensation of grandeur, not to be shared. Paras are friends and companions to each other. They co-operate delightedly in attempting to make normals like themselves. A paranoiac would not want anyone to share his greatness!"

Calhoun considered, and then agreed.

"Since you've said it, I see that it must be so. But my question remains. Madness involves delusions. But paras organize themselves. They make plans and take different parts in them. They act rationally for purposes they agree on—such as assassinating me. But how can they act rationally if they have delusions? What sort of delusions do they have?"

The Minister for Health said thinly:

"Only what horrors out of the jungles might suggest! I ... I cannot listen, Dr. Lett. I cannot watch, if you intend to demonstrate!"

The man with thick glasses waved an arm. The Minister for Health went hastily out. Dr. Lett made a mirthless sound.

"He would not make a medical man! Here is a para in this aseptic room. He is an unusually good specimen for study. He was my assistant and I knew him when he was sane. Now I know him as a para. I will show you his delusion."

He went to a small culture oven and opened the door. He busied himself with something inside. Over his shoulder he said with unction:

"The first settlers here had much trouble establishing a human-use ecology on this world. The native plants and animals were useless. They had to be replaced with things compatible with humans. Then there was more trouble. There were no useful scavengers—and scavengers are essential! The rat is usually dependable, but rats do not thrive on Tallien. Vultures—no. Of course not. Carrion beetles ... Scarabeus beetles ... The flies that produce maggots to do such good work in refuse disposal.... None thrive on Tallien Three! And scavengers are usually specialists, too. But the colony could not continue without scavengers! So our ancestors searched on other worlds, and presently they found a creature which would multiply enormously and with a fine versatility upon the wastes of our human cities. True, it smelled like an ancient Earth-animal called skunk—butyl mercaptan. It was not pretty—to most eyes it is revolting. But it was a scavenger and there was no waste product it would not devour."

Dr. Lett turned from the culture oven. He had a plastic container in his hand. A faint, disgusting odor spread from it.

"You ask what the delusions of para may be?" he grinned derisively. He held out the container. "It is the delusion that this scavenger, this eater of unclean things, this unspeakable bit of slimy, squirming flesh—paras have the delusion that it is the most delectable of foodstuffs!"

He thrust the plastic container under Calhoun's nose. Calhoun did not draw in his breath while it remained there. Dr. Lett said in mocking admiration:

"Ah! You have the strong stomach a medical man should have! The delusion of the para is that these squirming, writhing objects are delightful! Paras develop an irresistible craving for them! It is as if men on an Earth-like world develop an uncontrollable hunger for vultures and rats and—even less tolerable things. These scavengers—paras eat them! So normal men would rather die than become paras!"