OK, I'm back.
Smitten, something is definitely
functioning differently. It's not a simple matter of flesh types, because I would agree with your Bella comments, that wouldn't make sense.
If it was a simple matter of flesh type, then all areas of mucous membrane would be the same. That actually makes a great deal of sense to me. It sounds logical, and that is the way we are built. I've even heard of a woman having her lip repaired by transplanting membrane from another area (ahem).
So we could say human flesh is tranformed into vampire flesh, and there may even be translations of flesh type into a corresponding type. That makes a lot of sense. That should be the way things work. If areas of mucous membrane have a slightly different quality when vampirized, or even if the don't, then regardless of location the flesh should be very similar.
The problem, though, is that the
functional ability would change once the skin was vampirized. With the mouth this is no big deal, the vamp can still talk, secrete venom saliva, bite, drink blood, etc. The mouth still functions. With the sexual organs, though, you would have a complete loss of function if everything was turned to stone. Similar flesh translated to vampire flesh doesn't create a problem in one area, but it does in another.
Bear with me a bit.
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A Theory of Vampire Wood
by corona
Copyright MMXII
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One of the more difficult things to imagine is how the Denalis have sex with men. When you think about it, though, if the Denalis have problems (impenetrable marble walls), then Edward would have a problem as well. This is, after all, vampire flesh that is being stretched and engorged through an increase in venom pressure (or blood, depending on your theory). This isn't a muscle being flexed, it a flesh tube being filled with fluid. The flesh tube expands because of hydraulic pressure. In Edward's case, this is vampire flesh, and yet the process appears to be very similar. Arteries open up letting blood in (or whatever vampire fluid is used) and veins constrict reducing the outward flow.
So, even if we assume that vamp-to-vamp is completely like human-to-human, it still doesn't work for sex. The process is the same for Edward as it is for human men. Inflation is based purely on increased fluid pressure, we react to exactly the same force, which has nothing to do with being or not being a vampire. In fact, the blood theory for male vampires means that inflation is due to exactly the same fluid. But, what works for humans won't work for Edward IF he is built like a titanium tank. The only way it could work for Edward is either a) enormous pressure that is vastly greater than a human's (and there are a number of problems with that), or more likely b) his vampire skin there somehow acts similarly to a human's, it is actually quite flexible. I can't explain why, but it is. That doesn't mean it's still human, just that it is still elastic, and possibly the only place on his body that still is. Which is why B&E do not have a problem there on the island.
[BTW, Smitten, look at the honeymoon image in your signature. Both hands on the headboard? Yep, that's how I imagined it too. That position is only possible under option B, though, NOT option A. This picture is worth a thousand rhetorical thrusts.]
And if Edward is like the rest of us, then he maintains the ability to have sex exclusively based on fluid pressure, the exact same way human men are built. His vampire skin there may be indestructible, but his organ is standing at attention for only one reason, it is filled with either blood or venom, period. There is nothing special about the physical qualities of venom either, it is a fluid that flows like water and Edward can fill a hypodermic needle with it. Therefore, there are physical limitations based upon that, unless he somehow gains a hardened shell when ready and is no longer reliant on fluid pressure.
Female vampires, therefore, must have elastic qualities too, or there cannot be sex. Male vampires cannot overcome a resistance greater than the hydraulic pressure that is keeping their popsicle of death upright, and they are just like human men in that respect. If the vampire flesh swells soley due to the increased concentration and pressure of fluids, then it is
completely reliant on those fluids for rigidity, not their vampire flesh. Male vampires would not have
any significant advantage of rigidity over male humans.
This doesn't make things complex, it actually makes things very simple.
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Smitten's Auditory Evidence
Smitten, those are very good points. Let me bring in another view on that, Edward Cullen himself:
The Real Edward Cullen wrote:Bella, my heart, you said this boat would take us away from the noise in our house. Yet, I must point out, that you, my love, are rather noisy and I am certain that you would make those noises in a boat, in the water, in our home, or wherever we may be together.
But I accept your gift with much gratitude and love.
Bella is loud.
We don't know if these Bella noises are vocalized or vampiric impact sounds, Edward didn't elaborate. If they are impact sounds, then I rest my case. If these are vocal sounds, then the question is moot, Bella couldn't hear the other sounds anyway over her own cacophony.
I accept Edward as the authority on this.