st continued. "It's used
quite frequently in medicine, as Dr. Smathers will tell you. For
instance, beryllium ions in the body can be deadly; beryllium poisoning
is nasty stuff. But if the patient is treated with the proper chelating
agent, the ions are surrounded and don't do any more damage. They're
still there, but now they're harmless, you see."

"Well, then," said the colonel, "just what did this stuff in the fruit
do?"

"It sequestered the iron ions in the body. They couldn't do their job.
The body had to quit making hemoglobin, because hemoglobin needs iron.
So, since there was no hemoglobin in the bloodstream, the patient
developed sudden pernicious anemia and died of oxygen starvation."

Colonel Fennister looked suddenly at Dr. Smathers. "I thought you said
the blood looked normal."

"It did," said the physician. "The colorimeter showed extra hemoglobin,
in fact. But the chelating agent in the fruit turns red when it's
connected up with iron--in fact, it's even redder than blood hemoglobin.
And the molecules containing the sequestered iron tend to stick to the
outside of the red blood cells, which threw the whole test off."

"As I understand it, then," said Major Grodski, "the antidote for the
... uh ... chelating agent is magnesium?"

"That's right," said Dr. Petrelli, nodding. "The stuff prefers magnesium
ions to ferrous ions. They fit better within the chelating ring. Any
source of magnesium will do, so long as there's plenty of it. MacNeil
was using milk of magnesia, which is the hydroxide, for 'gastric
acidity'. It's changed to chloride in the stomach. And he was using
Epsom salts--the sulfate, and magnesium citrate as laxatives. He was
well protected with magnesium ions."

"We tried it ourselves first, naturally," said Dr. Pilar. "We haven't
had any ill effects for two days, so I think we'll be able to make it
until the ship comes."

Major Grodski sighed. "Well, if not, I'll at least die with a full
stomach." He reached for another banana-pear, then looked over at
Petrelli. "Pass the salt, please."

Silently and solemnly, the chemist handed him the Epsom salts.

THE END

+--------------------------------------------------------------+
| Transcriber's Note and Errata |
| |
| This etext was produced from Astounding Science Fiction, May |
| 1959. Extensive research did not uncover any evidenc