Arnold Netter (1855–1936) was a paediatrician who clinically applied the progress that his Pasteurian contemporaries had made possible through their bacteriological discoveries. From a neurological point of view, he brought looking for Kernig's sign into mainstream use to confirm the clinical diagnosis of meningitis and made diagnostic lumbar puncture systematic. He was one of the first to cure meningococcal and pneumococcal meningitis, long before the era of antibiotics, using subtractive lumbar puncture and intraspinal serotherapy. Netter's attentive vigilance enabled him to recognise, from its onset, the first poliomyelitis epidemic of the 20th century which took place in the summer of 1909. He described the clinical and epidemiological characteristics, identifying the viral rather than microbial origin.

Netter detected the first cases of encephalitis lethargica in Paris in 1918. The disease had been described by Constantin von Economo (1876–1931) in Vienna the previous year. Netter spent fifteen years studying this new disease, which caused a pandemic a century ago. He filled in the clinical picture and used his understanding of cerebrospinal fluid and pathological anatomy to enhance knowledge and improve treatment of this neurological pathology.