On the contrary, my heart began to thump and my lungs seemed unable to draw sufficient air for my blood.

This sense of suffocation was terrorizing, and every thump of the heart threatened to burst my already bursting lungs.
After what seemed hours, and after what, out of my countless succeeding experiences in the jacket I can now fairly conclude to have been not more than half-an-hour, I began to cry out, to yell, to scream, to howl, in a very madness of dying.

The trouble was the pain that had arisen in my heart.

It was a sharp, definite pain, similar to that of pleurisy, except that it stabbed hotly through the heart itself.
To die is not a difficult thing, but to die in such slow and horrible fashion was maddening.

Like a trapped beast of the wild, I experienced ecstasies of fear, and yelled and howled until I realized that such vocal exercise merely stabbed my heart more hotly and at the same time consumed much of the little air in my lungs.
I gave over and lay quiet for a long time--an eternity it seemed then, though now I am confident that it could have been no longer than a quarter of an hour.