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Physiology & Medicine / What determines the colour of reflections when an animals' eyes are illuminated?

« on: 30/11/2015 22:45:33 »

When I walk the dogs in the dark morning, with my head torch I can see their eyes reflect with a bluey white colour, and the pair of of foxes in the church grounds that have a yellow reflection.  There don't seem to be any cats about, but I know from flash photography that people have red reflections.

Why do different animals have different coloured eye reflections?

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Physiology & Medicine / How do bowels transport gas separately from solids?

« on: 07/11/2015 11:36:30 »

I do like a couple of real ales, but subsequently suffer from their flatulent effect on me.  On the up side, it does make me marvel at the ability of my bowels to separate the gas from solids, and transport it against gravity (which would be expected to pull the heavier solids down first) to my anus to be released.

How do bowels do this?
Can the process be mimicked with a manmade system? Would he ability to separate gas from solid and transport it separately within a single closed tube have a scientific or engineering application?