it without damaging the body of the host. But now a
flareup had occurred. The _Lancet_ brought in supplies of the
antibiotic, and Tiger Martin spent two days showing Singallese
physicians how to control further outbreaks with modern methods of
immunization and antisepsis.

Another planet called for a patrol ship when a bridge-building disaster
occurred; one of the beetle-like workmen had been badly crushed under a
massive steel girder. Dal spent over eighteen hours straight with the
patient in the _Lancet_'s surgery, carefully repairing the creature's
damaged exoskeleton and grafting new segments of bone for regeneration
of the hopelessly ruined parts, with Tiger administering anaesthesia and
Jack preparing the grafts from the freezer.

On another planet Jack faced his first real diagnostic challenge and met
the test with flying colors. Here a new cancer-like degenerative disease
had been appearing among the natives of the planet. It had never before
been noted. Initial attempts to find a causative agent had all three of
the _Lancet_'s crew spending sleepless nights for a week, but Jack's
careful study of the pattern of the disease and the biochemical
reactions that accompanied it brought out the answer: the disease was
caused by a rare form of genetic change which made crippling alterations
in an essential enzyme system. Knowing this, Tiger quickly found a drug
which could be substituted for the damaged enzyme, and the problem was
solved. They left the planet, assuring the planetary government that
laboratories on Hospital Earth would begin working at once to find a way
actually to rebuild the damaged genes in the embryonic cells, and thus
put a permanent end to the disease.

These were routine calls, the kind of ordinary general medical work that
the patrol ships were expected to handle. But the visits to the various
planets were welcome breaks in the pattern of patrol ship life. The
_Lancet_ was fully equipped, but her crew's quarters and living space
were cramped. Under the best conditions, the crewmen on patrol ships got
on each other's nerves; on the _Lancet_ there was an additional focus of
tension that grew worse with every passing hour.

From the first Jack Alvarez had made no pretense of pleasure at Dal's
company, but now it seemed that he deliberately sought opportunities to
annoy him. The thin Blue Doctor's face set into an angry mold whenever
Dal was around. He would get up and leave when Dal entered th