"Two Scotsmen" joke

Two Scotsmen had been pals since childhood and had shared everything over the years. One day, Angus won a rare bottle of Scotch in a door prize.
Immediately, Jock says "Open it up and we'll have a dram."
"Naw, ah'm goin' tae save it for a special occasion."
Birthdays came and went, his anniversaries came and went, but Jock could never get Angus to open the bottle.
Finally Angus had a heart attack, and was laying on his deathbed. He motioned for his old friend to come closer. "Jock, remember that rare bottle of Scotch I won?"
"Aye, ah certainly do, Angus!"
"Weell, ah like ye tae do me a favor Jock, my dear friend."
"Aye, anything ye ask Angus."
"When ah'm dead, wid ye take that bottle an' open it up--"
"Aye, Angus, then what?"
"Wid ye pour it over ma grave?"
"Pour it over yer grave? My god Angus. It's 40 year old Scotch! But I'll do it for ye."
"Oh, ye're a real pal Jock, and ah'll appreciate that."
Jock says, "There's just one thing Angus, wid ye mind if ah filter it through my kidneys first?"