ens and tried to culture
them. Some of his cultures had grown, though they might be nothing but
unknown Martian fungi or bacteria. Mars was dry and almost devoid of
air, but plants and a few smaller insects had survived and adapted. It
wasn't by any means lifeless.

Without a microscope, he could do little but depend on his files of
cases. But today there was new evidence. A villager had filched an Earth
_Medical Journal_ from the tractor driven by Chris Ryan and forwarded it
to him. He found the black specks mentioned in a single paragraph, under
skin diseases. Investigation of the diet was being made, since all cases
were among people eating synthetics.

There was another article on aberrant cases--a few strange little
misbehaviors in classical syndromes. He studied that, wondering. It had
to be the same thing. Diet didn't account for the fact that the specks
appeared only when the patient was near death.

Nor did it account for the hard lump at the base of the neck which he
found in every case he could check. That might be coincidence, but he
doubted it.

Whatever it was, it aggravated any other disease the patient had and
made seemingly simple diseases turn out to be completely and rapidly
fatal. Once syphilis had been called "The Great Imitator". This gave
promise of being worse.

He shook his head, cursing his lack of equipment. Each month more people
were dying with these specks--and he was helpless.

The concealed door broke open suddenly and a boy thrust his head in.
"Doc, there's a man here from Einstein. Says his wife's dying."

The man was already coming into the room.

"She's powerful sick, Doc. Had a bellyache, fever, began throwing up.
Pains under her belly, like she's had before. But this time it's awful."

Doc shot a few questions at him, frowning at what he heard. Then he
began packing the few things that might help. There should be no
appendicitis on Mars. The bugs responsible for that shouldn't have
adapted to Mars-normal. But more and more infections found ways to cross
the border. Gangrene had been able to get by without change, it seemed.
So far, none of the contagious infections except polio and the common
cold had made the jump.

This sounded like an advanced case, perhaps already involving
peritonitis.

So far, he'd been lucky with penicillin, but each time he used it with
grave doubts of its action on the Mars-adapted patients. If the appendix
had burst, however, it was the only