In the painting of The Last Judgment, Bartholomew holds his skin from his martyredom. Shown here (facsimile detail extract above), Michelangelo painted the skin as a self-portrait.
Michelangelo wrote the verse (below) about his fear of damnation following his death ("a double-death"), and of his final view of 'beauty' as a means to an end.
"My life's journey has finally arrived, after a stormy sea, in a fragile boat, at the common port, through which all must pass to render an account and explanation of their every act, evil and devout.
So now I fully recognize how my fond imagination, which made art for me an idol and a tyrant, was laden with error, as is that which all me desire to their own harm.
What will now become of my former thoughts of love, empty yet happy, if I am now approaching a double death? Of one I am quite certain, and the other threatens me.
Neither painting nor sculpting can any longer quieten my soul, turned now to that divine love which on the cross, to embrace us, opened wide its arms."
From Michelangelo: The Poems, translation by C. Ryan, J. M. Dent,1996.