ed to know.

"Nothing," Dal said. "Nothing at all. I did autopsies on the six that
you brought up here and made slides of every different kind of tissue I
could find. The anatomy is perfectly clear cut, no objections there.
These people are very similar to Earth-type monkeys in structure, with
heart and lungs and vocal cords and all. But I can't find any reason why
they should be dying. Any luck with the cultures?"

Jack shook his head glumly. "No growth on any of the plates. At first I
thought I had something going, but if I did, it died, and I can't find
any sign of it in the filtrates."

"But we've got to have _something_ to work on," Tiger said desperately.
"Look, there are some things that always measure out the same in _any_
intelligent creature no matter where he comes from. That's the whole
basis of galactic medicine. Creatures may develop and adapt in different
ways, but the basic biochemical reactions are the same."

"Not here, they aren't," Dal said. "Take a look at these tests!"

They carried the heap of notes they had collected out into the control
room and began sifting and organizing the data, just as a survey team
would do, trying to match it with the pattern of a thousand other
living creatures that had previously been studied. Hours passed, and
they were farther from an answer than when they began.

Because this data did not fit a pattern. It was _different_. No two
individuals showed the same reactions. In every test the results were
either flatly impossible or completely the opposite of what was
expected.

Carefully they retraced their steps, trying to pinpoint what could be
going wrong.

"There's _got_ to be a laboratory error," Dal said wearily. "We must
have slipped up somewhere."

"But I don't see where," Jack said. "Let's see those culture tubes
again. And put on a pot of coffee. I can't even think straight any
more."

Of the three of them, Jack was beginning to show the strain the most.
This was his special field, the place where he was supposed to excel,
and nothing was happening. Reports coming up from the planet were
discouraging; the isolation techniques they had tried to institute did
not seem to be working, and the spread of the plague was accelerating.
The communiques from the Bruckians were taking on a note of desperation.

Jack watched each report with growing apprehension. He moved restlessly
from lab to control room, checking and rechecking things, trying to find
some s