Thinking question

"From this state he was awakened -- ages later, it seemed to him -- by the pain of a sharp pressure upon his throat, followed by a sense of suffocation. Keen, poignant agonies seemed to shoot from his neck downward through every fiber of his body and limbs. These pains appeared to flash along well defined lines of ramification and to beat with an inconceivably rapid periodicity. They seemed like streams of pulsating fire heating him to an intolerable temperature. As to his head, he was conscious of nothing but a feeling of fullness -- of congestion. These sensations were unaccompanied by thought. The intellectual part of his nature was already effaced; he had power only to feel, and feeling was torment."
 I thought this is a good description of what suffocating while hanging by one's neck would feel like. Bierce did a good job and gave good details on exactly what the pain would feel like. He also gave a good description of what a hallucination induced by lack of oxygen would be like. What I wonder is if he just came up with that on his own. How would he know if someone would hallucinate if they were hung? How could He know that a hallucination would seem so long in such a short amount of time? Why did Bierce add the hallucination in in the first place, was it because he wanted to try to show the reader what a hallucination would be like or was it to give the reader a false sense of relief? I personally think it's the latter.