Douglas Argyll Robertson's (1837-1909) experimental work with physostigmine in 1863 sharpened his knowledge of the innervation of the internal muscles of the eye. So he was ideally prepared in 1869 to analyse the conundrum when he saw patients with spinal cord disease who had lost the response to light even though accommodation to near objects was normal. By translating his knowledge of basic science to a clinical problem he drew attention to this phenomenon, known subsequently as the Argyll Robertson pupil that came to be considered pathognomonic of tabes dorsalis, general paresis and neurovascular syphilis.