The author underlines the part of Pierre Salomon Ségalas in experimental physiology as his works are written for ever in the famous Journal de physiologie of François Magendie and insists upon his creation of the "speculum for urethra" which became the precursor of our modern devices. Ségalas practised urology as speciality while he had wide knowledge in physical chemistry and medicine whose traces can be found in the meetings of the "Académie de Médecine" he often attended. He is the example of a complete medical practitioner of the first half of the XIXth century as he created the idea of an exclusive speciality to practise.