"The atmospheric problem is even easier. Carbon dioxide and carbon monoxide are the only things we have to worry about. We have a scrubbing machine that absorbs the breathed-out carbon dioxide from the atmosphere and pumps it out into the sea. Carbon monoxide — which we could more or less eliminate if we forbade cigarette smoking, only we don't want a mutiny on our hands when we're three hundred feet down — is burned to monoxide by a special heater and then scrubbed as usual. And even that hardly worries me, I've a very competent engineman who keeps those machines in tip-top condition." He sighed. "I've a surgery here that will delight your heart, Dr. Carpenter. Operating table, dentist's chair, the works, and the biggest crisis I've had yet is a cigarette burn between the fingers sustained by a cook who fell asleep during one of my lectures."
"Lectures?"
"I've got to do something if I'm not to go off my rocker. I spend a couple of hours a day keeping up with all the latest medical literature, but what good is that if you don't get a chance to practice it? So I lecture. I read up on places we're going to visit, and everyone listens to those talks. I give lectures on general health and hygiene, and some of them listen to those. I give lectures on the perils of overeating and underexercise, and no one listens to those. I don't listen to them myself. It was during one of those that the cook got burned. That's why our friend Henry, the steward, adopts his superior and critical attitude toward the eating habits of those who should obviously be watching their eating habits. He eats as much as any two men aboard but owing to some metabolic defect he remains as thin as a rail. Claims it's all due to dieting."