erably. He cried out at them. Blood vessels in his
temples throbbed with his hatred. He cursed them.

* * * * *

"I point out one thing more," said Dr. Lett. "I would like to have the
co-operation of the Interstellar Medical Service. I am a citizen of
this planet and not without influence. But I would like to have my
work approved by the Med Service. I submit that in some areas on
ancient Earth, iodine was put into the public water-supply systems to
prevent goiters and cretinism. Fluorine was put into drinking water to
prevent caries. On Tralee the public water supply has traces of zinc
and cobalt added. These are necessary trace elements. Why should you
not concede that here there are trace elements or trace compounds
needed----"

"You want me to report that," said Calhoun, flatly. "I couldn't do it
without explaining--a number of things. Paras are madmen, but they
organize. A symptom of privation is violent yawning. This ...
condition appeared only six months ago. This planet has been colonized
for three hundred years. It could not be a naturally needed trace
compound."

Dr. Lett shrugged, eloquently and contemptuously.

"Then you will not report what all this planet will certify," he said
curtly. "My vaccine----"

"You would not call it a vaccine if you thought it supplied a
deficiency--a special need of the people of Tallien. Could you give me
a small quantity of your ... vaccine?"

"No," said Dr. Lett blandly. "I am afraid you are not willing to be
co-operative. The little of my vaccine that is available is needed for
high officials, who must be protected from the para condition at all
costs. I am prepared to make it on a large scale, though, for the
whole population. I will see, then, that you have as much of it as you
need."

Calhoun seemed to reflect.

"No," he admitted, "I'm not ready to co-operate with you, Dr. Lett. I
have a very uncomfortable suspicion. I suspect that you carry a small
quantity of your vaccine with you all the time. That you cannot bear
the idea of being without it if you should need it. I say that because
it is a symptom of other ... similar conditions. Of other ... abnormal
appetites."

Dr. Lett had been bland and grinning in mockery. But the amusement
left his face abruptly.

"Now ... what do you mean by that?" he demanded.

Calhoun nodded his head toward the para behind the glass wall.

"That poor devil nearly yawned his head off before yo