re carried by
electromagnetic radiation of wildly varying wave-lengths, are not likely
to be the fabled music of the spheres. He waited.

* * * * *

In fifteen minutes a different voice came from the speaker.

"_Med Ship Aesclipus! Med Ship Aesclipus!_"

Calhoun answered and the voice said anxiously;

"_'Sorry about the challenge, but we have the blueskin problem always
with us. We have to be extremely careful! Will you come in, please?_"

"I'm on my way," said Calhoun.

"_The planetary health authorities,_" said the voice, more anxiously
still, "_are very anxious to be cooperative. We need Med Service help!
We lose a lot of sleep over the blueskins! Could you tell us the name of
the last Med Ship to land here, and its inspector, and when that
inspection was made? We want to look up the record of the event to be
able to assist you in every possible way._"

"He's lying," Calhoun told Murgatroyd, "but he's more scared than
hostile."

He picked up the order-folio on Weald Three. He gave the information
about the last Med Ship visit. He clicked off.

"What?" he asked, "is a blueskin?"

He'd read the folio on Weald, of course, but as the ship swam onward
through emptiness he went through it again. The last medical inspection
had been only perfunctory. Twelve years earlier--instead of three--a
Med Ship had landed on Weald. There had been official conferences with
health officials. There was a report on the birth-rate, the death-rate,
the anomaly-rate, and a breakdown of all reported communicable diseases.
But that was all. There were no special comments and no overall picture.

Presently Calhoun found the word in a Sector dictionary, where words of
only local usage were to be found.

"Blueskin; Colloquial term for a person recovered from a plague which
left large patches of blue pigment irregularly distributed over the
body. Especially, inhabitants of Dara. The condition is said to be
caused by a chronic, non-fatal form of Dara plague and has been said to
be non-infectious, though this is not certain. The etiology of Dara
plague has not fully been worked out. The blueskin condition is
hereditary but not a genetic modification, as markings appear in
non-Mendellian distributions...."

Calhoun puzzled over it. Nobody could have read the entire Sector
directory, even with unlimited leisure during travel between solar
systems. Calhoun hadn't tried. But now he went laboriously through