Napoleon Cybulski is widely regarded as a pioneer of electroencephalography and endocrinology in Poland and the world. In 1895, with his pupil :pl:Władysław Szymonowicz|Władysław Szymonowicz, he discovered the hormonal interactions of the adrenal medulla and isolated adrenaline. He called the substance nadnerczyna. In 1890 Cybulski carried out one of the first-ever EEG recordings of the cerebral cortex. Working with Adolf Beck, he conducted pioneering research on electroencephalographic waves. Under Cybulski’s supervision, Beck made pioneering studies of cerebral-cortex activity in response to peripheral-nerve stimulation in dogs and monkeys, using electrodes placed on the skull to record changes in electric potential. In this way they invalidated William Horsley’s notion that these changes reflected the activity of skull muscles. By further analyses of potential changes, they mapped out sensory regions of the cerebral cortex. They also provided evidence that the amplitude of signals depended on the strength and kind of sensory stimulus and on the depth of anesthesia. They suspected that brain function was mediated by neurons' bioelectrical activity. Their studies on brain mapping and nerve stimulation were absolutely innovative, since they were unfamiliar with earlier research done by Richard Caton on changes in bioelectrical activity of the dog brain during sleep, activity, and changes in behavior. Again working with Beck, Cybulski showed that every taste sensation in the tongue was caused by a separate kind of receptor. He gave a description of the difference between afferent and efferent impulses entering and leaving the spinal cord based on recordings from dorsal and ventral roots. In 1914 Napoleon Cybulski and S. Jeleńska-Macieszyna photographed EEG recordings of experimentally induced seizures. Cybulski was one of the first physiologists to register and describe the blood flow linear velocity of the carotid artery and the femoral artery. Among his other discoveries was establishing that an increase in intracranial pressure causes disturbances in blood flow to the brain. Cybulski authored around 100 medical research papers. He initiated research on hypnosis in Poland. Some of his theses in O hypnotyzmie ze stanowiska fizyjologicznego anticipate ideas of Sigmund Freud and make him a precursor of the concept of the unconscious.
Social questions
Apart from medicine, Cybulski was also interested in a range of social questions and published books and articles such as Czy państwo i społeczeństwo mają obowiązek popierać naukę?, W sprawie organizacji gospodarstw włościańskich and Nauka wobec wojny. He was a staunch advocate of allowing women to study medicine. In 1891, Cybulski and a pioneering Polish bacteriologist, Odo Bujwid, established the first girls' gimnazjum in Kraków.