cowcreekgeek, thank you for posting the references. It looks like they are from the same one you sent me last week (sorry I never got back to you to thank you for it before), which I have printed out and am reading through. According to that paper, quite a bit is known about pain perception in chickens, and the overwhelming evidence is that they do indeed have the neuroanatomy and physiology for pain perception, and it is actually quite similar to pain perception in humans and other mammals. I am hoping to find the time to start a separate thread to discuss pain perception in chickens, using that paper as a spring board.
So yes, vivisection on chickens is currently legal, but there have been times and places in history where even human vivisection without anesthesia was acceptable (as done on slaves, POW's, and Jews). But make no mistake, those people suffered. So do chickens.
Best of luck to Rags. PAchickenlover, I am glad to hear you are interested in avian veterinary medicine. There is obviously a great and growing need for vets trained to treat chickens with appropriate pain relief.