the bottom quantified: out of vein, cooking with urine
It was the first and only time ever that Gately I.V.'d narcotics so many times in one arm that he ran out of arm-vein and had to switch to the other arm.
Context
The bottom rendered as pure physical data, no sermon: so many injections in one arm that the veins give out and he moves to the other, then — the distilled water gone — cooking the next shot up out of the piss they've been sitting in. The tell is the smallest clause, "appeared to himself to be repulsed" — even the disgust is at one remove, observed rather than felt, which is how far the Substance has taken the man from his own reactions. This is the lived floor under every AA position Gately will later hold; he earned the doctrine here, on a urine-corroded oak floor.