Giovanni Vitali: Discoverer of the paratympanic organ.

One-hundred years ago, the Italian anatomist Giovanni Vitali reported the discovery of the paratympanic organ, a sense organ in the middle ear of birds, in two issues of the Anatomischer Anzeiger (1911, 1912). In this minireview, we summarize Vitali's biography, and examine the scientific impact of his discovery of this sense organ. We also compile - for the first time - the entire bibliography of published papers on the paratympanic organ. Vitali described the ontogenetic development of this sense organ, examined its distribution among species, recognized its evolutionary relationship with the spiracular sense organ of fishes, and he developed the theory that it functions as a detector of changes in air pressure. He was the first to postulate that the paratympanic and spiracular sense organs were homologous organs that originate from homologous placodes - currently a hotly debated topic. His morphological work indicating the sensory nature of the PTO was validated by subsequent ultrastructural studies. Vitali's discovery of the paratympanic organ prompted his nomination for the Nobel Prize in 1934. Nevertheless, the paratympanic organ and the presumed barometric sense of hundreds of billions of living birds have failed to receive the recognition they deserve. Conclusive evidence of the function of the paratympanic organ remains a formidable challenge in vertebrate sensory physiology.