Ray Wilhite posted this gorgeous image on a Facebook thread, and we're re-posting it here with his permission. It's taken from a poster that Ray co-authored (Roberts et al. 2016). We're looking here at a coronal cross-section of a hen (age not specified), with anterior to the left.
Mike Taylor (Mon,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: