"We lose a lot of otherwise promising antibiotics here, too," Gunn said. "Most of them turn out to be too toxic to be used in or even on the human body. We've had Hansen's bacillus knocked out a thousand times in the test-tube only to find here that the antibiotic is much more quickly fatal in vivo than is leprosy itself. But once we're sure that the drug isn't toxic, or that its toxicity is outweighed by its therapeutic efficacy, it goes out of our shop entirely, lb hospitals and to individual doctors for clinical trial. We also have a virology lab in Vermont where we test our new drugs against virus diseases like the flu and the common cold. It isn't safe to operate such a lab in a heavily populated areas like the Bronx."

"It's much more elaborate than I would have imagined," Paige said. "But I can see that it's well worth the trouble. Did you work out this sample screening technique here?"

"Oh, my, no," Gunn said, smiling indulgently. 'Waksman, the discoverer of streptomycin, laid down the essential procedure decades ago. We aren't even the first firw to use it on a large scale; one of our competitors did that and found a broad-spectrum antibiotic called chloramphenicol with it, scarcely a year after they'd begun. That was what convinced the rest of us that we'd better adopt the technique before we got shut out of the market entirely. A good thing, too; otherwise none of us would have discovered tetracycline, which turned out to be the most versatile antibiotic ever tested."

Farther down the corridor a door opened. The squall of a baby came out of it, much louder than before. It was not the sustained crying of a child who had had a year or so to practice, but the shortbreathed "ahla, ahla, ahla," of a newborn infant.

Paige raised his eyebrows. "Is that one of your experimental animals?"

"Ha, ha," Gunn said. "We're enthusiasts in this business, Colonel, but we must draw the line somewhere. No, one of our technicians has a babysitting problem, and so we've given her permission to bring the child to work with her, until she's worked out a better solution."

Paige had to admit that Gunn thought fast on his feet. That story had come reeling out of him like so much ticker tape without the slightest sign of a preliminary doubletake. It was not Gunn's fault that Paige, who had been through a marriage which had lasted five years before he had taken to space, could distinguish the cry of a baby old enough to be out of a hospital nursery from that of one only days old.

"Isn't this," Paige said, "a rather dangerous place to park an infant with so many disease germs, poisonous disinfectants, and such things all around?"

"Oh, we take all proper precautions. I daresay our staff has a lower yearly sickness rate than you'll find in industrial plants of comparable size, simply because we're more aware of the problem. Now if we go through this door, Colonel Russell, we'll see the final step, the main plant where we turn out drugs in quantity after they've proved themselves."