I\'ve read the topics on blood and found it all very interesting, but it only briefly touched on digestion and I dont think that hijacking that thread is quite the proper thing to do.
First off, I\'ve heard a lot of Science vs Magic debates. As far as I\'m concerned, we\'re going with \'Plausible Explanation\'. No need to determine exact chemical formulas or anything, but \"It\'s magic!\" doesn\'t cut it either.
A few things to establish as \'known\' facts:
>Kran are silicon based.
>Kran eat mineral-rich objects (not necessarily only rocks)
>>Krans digest their food with the aid of powerful acid
>>Kran kitchens resemble alchemical laboratories
>Kran were originally created through magic
>Kran are extremely resistant to magic
>Their bodies are more rigid than those of Humans
>Kran are capable either of breathing underwater, or do not need to breathe (note: the PlaneShift website states that they can \'happily breathe underwater\')
>>If they do breathe underwater, they are amphibious.
So, let\'s run through the purposes of digestion:
1) Creates energy for the body to run
2) Absorb material for growth and rebuilding of damaged/worn parts
1 - Creating energy
As stated in another thread, there is not a suitable silicon equivalent for glucose/sugar in general. This means that Kran probably operate much like miniature power plants, burning elements and storing the heat until it is to be used.
Argument: If they stored too much heat, they would melt.
Counterpoint: Kran are magically created beings. It is possible that some sort of magic contains this heat and prevents it from destroying them.
Counterpoint: A Kran could have an organ filled with molten rock, coated with an extremely heat-resistant substance (like asbestos, but capable of withstanding greater temperatures). (Note: This does NOT mean lava blood. Too dangerous to be treated so lightly; probably a well-protected organ near their core. Their \'heart\', maybe?)
Counterpoint: If they store too much heat. Overeating might be dangerous, but it can be assumed that under normal conditions the heat doesn\'t reach dangerous levels.
Analysis: The first counterpoint I will talk about much later. The second is possible, but could mean that when a Kran dies or is severaly injured, the molten contents of their extra orgen spill out and either finish them or cause problems around them. The third is a simple question of whether they can store enough heat, and general plausability.
2 - Building material
Kran are silicon bsaed, and therefore would eat a lot of silicon-based foods. They could also nead other minerals to supplement their diet (much the same way as Humans need iron, sodium, potassium, and other elements in small amounts to maintain their health). This is ingested directly, broken down by powerful acid (unarguable - a stated fact), stored, and used as needed.
Arguments: Where does the acid come from?
Counterpoint: It\'s perfectly plausible that somewhere in the Kran anatomy is an organ that stores and mixes various chemicals, specifically acid and the components thereof. Sulfur (sulfiric acid) and Chlorine (Hydrochloric acid) may be very necessary parts of the Kran diet. The components of these might be held in seperate pouches and only combined to create acid in the stomach, or held in a seperate organ with much the same anti-acidic lining as the stomach.
Analysis: The internal workings of a Kran could and likely are more like a machine or alchemy lab than what a human is like. Kran \'cooking\' could consist of a granite slab with ground limestone \'sauce\', garnished with sulfur, and a glass of concentrated mineral sludge. For dessert, sand in saltwater, the consistency of oatmeal.
Beyond Digestion
The materials have to get to the part of the body where they are needed. This has two possibilities:
1) Animal-pattern distribution (blood)
2) Plant-pattern distribution
1- Animal-like food distribution
This requires some kind of circulatory system, but not necessarily \'blood\' in the sense that we may think of it. It may be some mixture of chemicals that can bind with the elements needed, or even several seperate networks. It might be a thick liquid, a mix of (to humans) toxic chemicals, or who knows what.
Argument: The network of blood vessels and capillaries needed would make Kran easy to chip, break, and shatter.
Analysis: A normal circulatory system is unlikely, for this exact reason.
2- Plant-like food distribution
Plants manage to distribute food throughout their bodies through use of Xylem and Phloem, one for water and one for minerals (in the case of Kran, it may be just one for minerals or one for minerals and one for some other vital semi-liquid). This would mean that part of the outer layer of the Kran is just dead material. They retain the ability to move because the inner \'core\' is still living and capable of moving - the dead material just moves with it, like a Human knight might wear their armor.
Arguments: (Insert scientific babble here)
Counterpoint: (Insert reasonable sounding scientific counterbabble here)
Analysis:
Beyond use
Anything that isn\'t used, well... comes back out. This doesn\'t necessarily mean that Kran (for lack of a more elegant wording) shit rocks. It could just be a lump of unused minerals that collects in their stomach and needs to be thrown up, like a hairball, every once in a while.
Argument: What about the acid in their stomach?
Counterpoint: They could have control over that, and only fill their stomach with acid while digesting something. For that matter, they could just eat a large amount of minerals, break it down, and just let it sit until it\'s used, adding what they do use when they need more.
If you want to add something, PLEASE do it in an organized fashion like this is. Define the issue/problem/point, give arguments for and against it. Makes it all a lot easier to sort out at the end of the day.