"Russell, Paige Russell, Army Space Corps."

"Thank you. If you'll accept my apologies for our preoccupation, Colonel Russell, I'll be glad to show you around our little establishment My name, by the way, is Harold Gunn, vice-president in charge of exports for the Pfitzner division."

"I'm importing at the moment," Paige said, holding out the soil samples. Gunn took them reverently and dropped them in a pocket of his jacket. "But I'd enjoy seeing the labs."

He nodded to the girl and the doors closed between them. He was inside.

The place was at least as fascinating as he had expected it to be. Gunn showed him, first, the rooms where the incoming samples were classified and then distributed to the laboratories proper. In the first of these, a measured fraction of a sample was dropped into a one litre flask of sterile distilled water, swirled to distribute it evenly, and then passed through a series of dilutions. The final suspensions were then used to inoculate test-tube slants and petri plates, containing a wide variety of nutrient media, which went into the incubator.

"In the next lab here. Dr. Aquino isn't in at the moment, so we mustn't touch anything, but you can see through the glass quite clearly we transfer from the plates and agar slants to a new set of media," Gunn explained. "But here each organism found in the sample has a set of cultures of its own, so that if it secretes anything into one of the media, that something won't be contaminated."

"If it does, the amount must be very tiny," Paige said "How do you detect it?"

"Directly, by its action. Do you see the rows of plates with the white paper discs in their centers, and the four furrows in the agar radiating from the discs? Well, each one of those furrows is impregnated with culture medium from one of the pure cultures. If all four streaks grow thriving bacterial colonies, then the medium on the paper disc contains no antibiotic against those four germs. If one or more of the streaks fails to grow, or is retarded compared to the others, then we have hope."

In the succeeding laboratory, antibiotics which had been found by the disc method were pitted against a whole spectrum of dangerous organisms. About 90 per cent of the discoveries were eliminated here, Gunn explained, either because they were insufficiently active or because they duplicated the antibiotic spectra of already known drugs. "What we call 'insufficiently active' varies with the circumstances, however," he added. "An antibiotic which shows any activity against tuberculosis or against Hansen's disease leprosy is always of interest to us, even if it attacks no other germ at all."

A few antibiotics which passed their spectrum tests went on to a miniature pilot plant, where the organisms that produced them were set to work in a deep aerated fermentation tank. From this bubbling liquor, comparatively large amounts of the crude drug were extracted, purified, and sent to the pharmacology lab for tests on animals.