I forgot these things, so to prevent confusion let me add them:
The bowel tolerance is 'increased' when the body has so much junk going on in the bloodstream/lymph and even actual stomach/gut that the AA starts getting used like crazy the instant it gets into you.
So on its path through your intestines sucking in water, there's less and less of it. Hence less water... less flushing... none at all if there's more 'demand' on it than there is substance.
Not flushing at all means your body 'had time' to digest 'what you gave it' compared to 'what it used right away.'
What Cathcart was measuring was what you could take not all at once, but in too-small-amounts-to-be-flushed that were repeated throughout the day, for however many days until the illness seemed conquered.
But even the bloodstream quantity of C doesn't reflect all the different tissue quantities. You can have ok blood counts and have deadly scurvy in a certain area of tissues still.
If you took 10g of C and flushed all but 1g of it, this could be despite that your body still desperately needs 50g (or more, ongoing). It's just that only so much of your bloody/lymph/gut can "get to" what you have ingested BEFORE the point where what you ingested is flushing itself out.
Oh yeah, the other thing: Aloe Vera (fillet leaf gel) is said to increase the absorption of ascorbic by 300%. I just saw a research ref on that today. I believe piperine also increases it somewhat but maybe not nearly as much.