This post will contain book spoilers for the entire series, including the Midnight Sun draft. Go Read.
In my plea for ideas last week, the lovely
RaShell came through f0r me with an excellent question about the physiology of our favorite vampires. I dug into some correspondence with Stephenie Meyer available at the
Lexicon and
TwilightMoms, as well as diving back into the series again (I LOVE when I have a good excuse to do that!).
So how does the whole thing work? I'm going to ask you to accept a certain about of "magic", because, after all, we're dealing with a fantasy world of undead, please don't go overboard with the logical stuff. I'm also only going to deal with vampires as they exist in the
Twilight universe.
Thanks to Alice, not to mention Bella's first hand account of her transformation, we know that, once bitten, the venom in a vampire's saliva begins to slowly move through the body. As it

moves, it both heals any damage done, and begins changing the body into the cold, hard, unliving body of a vampire. Eventually the venom reaches the heart, allowing it to flow to the entire body, before stilling the heart and leaving the newborn vampire "alive". The transformation takes approximately 3 days, but can be shortened by getting as much venom into the system as possible and as close to the heart as possible. Edward's bright idea of collecting his own venom into a cardiac syringe allowed him to get the venom directly into Bella's heart, allowing the venom to move through her body immediately.
The newborn vampire brings us to the basic thing for vampire physiology: Blood. Blood is everything for a vampire. Literally. Yes, yes, without it, us humans are pretty screwed, but that's not the point here. There's a significant point made that a newborn vampire is extremely strong, as a result of the remnants of their own human blood being in their system. Over time, this strength fades into the "normal" superhuman strength. (Can you imagine what Emmett was capable of as a newborn vampire??)
The blood doesn't just keep them alive, it literally powers everything. The strength, the speed,

the heightened senses, even the mental abilities. According to Q&A's with Stephenie Meyer, if you could cut into a freshly fed vampire, they would bleed, but otherwise not. This tells me that they drink the blood of their victim, whether human or animal, and it's absorbed into their body. They don't have the digestive system as we do, to put it as delicately as possible. The blood is simply absorbed and burned as they go about their lives, just like we do with food, the calories powering our bodies, giving us strength and stamina. They don't necessarily need to eat as often, though Edward mentions that the more often he feeds, the easier it is to curb his bloodlust.
Now for the fun part! Let's talk bodily fluids! From the books, we now there are a few. Vampires retain a few basic bodily fluids. According to Stephenie Meyer, all are composed basically of

venom. Saliva is the first, and the strongest composition of venom, since that's the direct application of it for the purposes of incapacitating their victims and beginning the conversion process. In the
Midnight Sun draft as well as Bella's experiences in
Breaking Dawn, we can gather that 'saliva' isn't entirely pure venom, as when the bloodlust strikes, there's a definite pooling of venom in their mouths, the vampire version of drooling, essentially. I have always taken from these accounts that the 'regular' saliva of a vampire is fairly diluted venom. After all, Edward made no move to stop Bella from taking a bite of that slice of pizza after he did. Perhaps it would have been a problem if she'd had a split lip or a cold sore, but then, Edward would have noticed that.

In
Breaking Dawn, we know that the fluid in their eyes is essentially venom also. Vampires are incapable of tears, but there is some fluid in the eye, enough to dissolve contact lenses in a matter of hours. We also become more aware that there is no 'waste' fluid to deal with.
And finally, the part I know you all REALLY want to know about....the one remaining body function. I assume we all took health class in middle school and/or had the birds and bees discussion with mom and dad, and I don't need to have a basic discussion of
how babies are made. Thanks to Bella's deliriously happy state, a few destroyed pillows and a broken headboard, we're left to assume (darn fade-t0-black!) that the mechanics of sex are the same. Remember back when I said that blood powers everything? Ahem. Yes. Not much different than a human male, right? Except, that I'd bet that those lovely vampire boys have a bit more control...as in 'on command'.
.....

Sorry, I'm back. Where was I? Oh, right, 'on command'. (Focus, ladies!) I'm sure at some point, instinct and desire take over and after a thoroughly satisfying and furniture destroying experience, another bodily fluid makes its appearance. Is it venomous? Probably, at least in that diluted state, but not enough to kill the little pieces of DNA required to make baby half-vampires. Here's part of where I'm asking you to accept a little magic. I'm sure many of you can come up with logical reasons why Edward's lil swimmers shouldn't be swimming anymore, but they do. Deal with it. Perhaps it's a blood thing, perhaps it's because sperm are produced constantly, as opposed to a pre-established number and cycle, like women. Perhaps it's a statement on the differences in the sexes. Either way, vampires pro-creating with humans isn't a new concept, perhaps because, regardless of the audience or story, a little vampire sexing is a good thing.
So, there we are, Kerry's Basic Vampire Physiology Course 101. I hope I answered your question, RaShell, if not, I could talk about Edward's...physiology a lot more, I'm sure.
If you missed it, last Thursday Amber and I, along with our guest blogger, Sabrina, began a
chapter by chapter discussion on Eclipse. Last week we discussed the preface, and this week we will dive in to chapter 1. Some of the future Twi-Theories may tie into events that happen in the book, but I'm also interested in other points you'd like to see discussed. Feel free to continue the discussion and suggest in the comments. Thank you!!