i believe it is some sort of euthanizing drug? is that what you mean? the vet found a vein beneath a wing and injected there...her passing was fairly quick, certainly peaceful.
i haven't yet developed a comfort level with both saying good bye to a hen and ending her misery myself, so this was what worked in our situation. i was grateful for the vet's assistance. now i can get her necropsy done, and focus on the new brood growing and the current flock. in some ways i am relieved it is over, but i will miss her terribly, walking around the garden with me, clucking, ever curious, as australorps can be, waiting for me to turn soil with my spade or fork.
i will post the necropsy findings here, as i will be fascinated to learn what was happening internally too. i will post when i have the results.