Physiology

"Jenny, you've got to stop trying to block with your arm. That's the third time this month you've nearly broken it. You can't block a club with your arm."

"It feels fine." Jenny replied, sitting back on the med-bay table. She looked down at the purplish-red blotch that spread from wrist to just below her elbow. The Doctor felt along the limb with quick, delicate fingers.

"You keep saying that, you know, but that doesn't mean I'm going to believe it. Just hold still."

He turned the arm from side to side. Jenny held her breath against the pain. The Doctor nodded to himself.

"Right, all three bones in shape, but I'm going to check for hairline fractures this time."

Jenny looked up.

"Three bones? Aren't there two bones in the forearm?"

"In a human forearm there are. In yours and mine it's a bit different. Here-" He flicked a button beside the table, and a small screen to the side lit up with a picture of her arm. Jenny studied it, fascinated. She moved her arm, and the image moved with it. She'd seen human bone-image scans, but she'd never been imaged before; she'd always been wary about letting people know she was different. Her bones didn't look like the ones she remembered. She wiggled her hand, and winced.

"Jenny, hold still." Her father said, glancing back at her in mock disapproval. "I need to look at this." He peered at the image, slipping on his glasses. Jenny stilled, watching as her father pointed.

"Here's the primary forebone, sort of like the radius in the humans, 'cept it's thinner and not connected to the hand the same way, and here's the secondary, this one that runs down the middle and connects the two on the outside. On the other side's the tertiary forebone. Now, it's not so bad if you break the primary forebone, but since the secondary bone connects the muscles for your hand to the ones for your arm it hurts like billy-oh if you break it. But, looks like you're lucky again. No cracks. Well, that's a relief then. So now we can see to the bruising."

"They're so thin." Jenny observed. The Doctor glanced at her, then back at the picture.

"Well, yes, like I said the bones are thinner than the human fore-limbs. But you really don't need as much bulk when you've got more supports taking the strain. Harder to break too, because they're more flexible than a great whopping chunk of brittle bone. That bruise…" He glanced at it again, then pulled out his sonic screwdriver and began to change settings. After a moment he shook his head, tucked it back in his pocket, and pulled open a drawer.

"It'll heal in a bit." Jenny reassured him.

"I know that, Jenny." He said distractedly, "But no sense letting it hurt the whole time while it's repairing, now is there? We can just-ah! There you are!" He pulled a small, dark wand from the drawer. It started to whirr slightly.

"Subdermal hemohemmorage reducer-modifier and cell-growth inducer. Malto bene. Here we go-" He ran the wand over her arm, which tingled with cold, then slowly warmed until it felt as if the area was fevered. She watched the bruise slowly pale. Now it was yellowish, now just a little pink. Her father smiled.

"That's better."

"It'd take eight hours to heal normally." Jenny said wonderingly, flexing her hand. Her father smiled lightly, watching her.

"And thirty-six if one of the bones had broken. See why I told you to stop using your arm to block?"

She shrugged, her face becoming calm and impassive.

Oh great. She's not listening to me.

"So, do you heal like me?"

"Mm, more or less. I heal just a bit faster, but I've also had…" He turned, moving to the shelves. "a few things done. Anyway, here's the rest of the skeleton." He clicked another button, and she could see a complete skeletal structure. She peered at it, then hopped off the table to look at it more closely.

"Neat."

"Yup."

She turned to watch her father. "So do you wake up when you die too?"

"Wake up when you die?" He let out a small laugh, turning to look at her. "Wake from the dead? That's a nice way to put it."

"I was dead, Father. Or I ought to have been. Then I woke up. How does that work?"

Her father shrugged. "Oh, you weren't all that dead. I've been dead, and believe me, it's a little more problematic." He strode across the room, finding something to occupy his hands as he talked. "It's called regeneration. When our bodies wear out or get damaged beyond repair, we regenerate. Of course usually we change too."

Jenny cocked her head. "Change?"

"Our appearances." He glanced up at her, smiling slightly. "Last time around I had a bit less hair, and a bit bigger ears. Picture me looking something like an Irish hit man. Time before that I was a bit of a poet, all willowy with long hair and green-green eyes?" He glanced upwards, considering, "No, hazel, they were hazel. Nearly forgot that. It's because our genetic code re-writes itself in order to make repairs, and things get changed along in the process. And it's not pleasant. So try not to get killed, all right? No sense overusing the privilege."

Jenny stared at him, her eyes wide.

"So any time we die-"

"Twelve times." Her father stilled. He turned to face her. "Twelve times we die and regenerate. Thirteen lives are given to us. A gift of Time Lord biology." He said the word 'gift' bitterly, the smile on his face small and pained. Jenny took a step forward. Why does it hurt him to think about that?

Then the Doctor drew a breath, and gave her a wide smile, covering the darkness.

"And it's a good thing we've got it, isn't it, since I am one of the more jeopardy friendly beings in the universe, and you're just as bad as I am, maybe even a bit worse, which is something I never thought I'd say. Anyway, you've got human anatomy and physiology in your head, let's get some stuff about your own body in there. Biology, anatomy, physiology. All the basics, strengths and weaknesses and tricks you can do. That kind of thing." He flicked on two screens, and pulled a pad from one of the drawers, handing it to her.

"These'll give you a better sense of bone and muscle structure. Some of this you probably know from experience, everyday life. Body temperature of sixteen degrees Celsius; we don't chill very easily, don't get hot very fast, got the respiratory bypass system and, of course, binary cardiovascular system. Pulse of seventy over seventy. Couple other things, I'll show you in a bit."

"Anything that can give me a tactical advantage?" Jenny asked. Her father shot her an annoyed glance.

"Not everything's about fighting, you know." Then he sighed. "Okay, things to remember, and you can call them 'advantages' if you like. We can go without oxygen for ten minutes, tops, before losing consciousness. We can handle a fall of about forty feet, but not much more than that. Our muscles are denser than the usual types, get a lot of tensile strength packed into small areas, so we can pretty much lift about…"

"Three times our weight?"

He nodded his head from side to side, considering. "And a little more, actually. How'd you know?"

Jenny grinned. "Won a prize on Setar Two. Benched three hundred and fifty pounds."

He nodded, eyebrows raised. "Very nice. That's muscle density at work. Three hundred and fifty?" He nodded, expression surprised and approving. Jenny smiled proudly.

"Anyway…" Her father leaned back against the counter, ticked facts off on his fingers. "Our range of vision goes from ten nanometers to three thousand nanometers along the electromagnetic spectrum, which is probably why you got the eye when you talked about the lovely colors on that stone to a few of those folks on Sakifrax; they didn't see the colors that you did. Hearing goes from ten hertz to about forty kilohertz. Which means opera is definitely not a pleasant experience. We can handle pressure levels equaling something like two thousand kilograms per square centimeter down to zero pressure. But I really wouldn't suggest mucking with the higher pressures, you feel off for days. Bodies can handle a lot of radiation, so don't worry too much about that. Oh, and our facial bones are a bit different, so they're not so easy to break, which is a good thing considering all the times I get punched in the nose. Still got a glass jaw though, me. Hope you didn't inherit that. Oh, and speaking of getting punched, don't get yourself punched on your left shoulder, especially on the collar bone, 'cause we've got a bundle of nerves right there, and you'll be out for hours with a good blow to that spot. We do badly with anything that's designed to act on the inflammatory and the pain-reception centers in terran life forms, anything that depresses brain function, and also anything with menthol or sallyic acid in it, so watch out for those. Don't let anyone give you aspirin, sedatives, mint tea, willow bark tea, or try to do surgery on you on Earth. That's never pretty. We have the ability to consciously control our heart rates, breathing rate, blood oxygen levels, and of course our respiratory bypass system, with a little training. Oh, and to sense changes in organ function and enzyme levels. We're rather like those odd little punching toys they made in the nineteen-fifties, actually. Knock us down and we pop back up again. Sums us up, just about." He grinned. "Any questions?"

"Yeah." Jenny said, turning back to him, "Can you show me the stuff about controlling my lungs and hearts?"