If you monitor the gallbladder for a longer time it will continue to fill becoming more expanded that its starting volume. The first dose of Epsom Salts will ensure that the stomach and small intestines are purge and if they are already empty it will contract and expand the gallbladder. The second dose will contract and then expand the gallbladder so that it is close to its maximum volume ready for the flush potion.
I have collected some useful information about the role of Epsom Salts on the following link:
//www.curezone.org/blogs/fm.asp?i=985355