protagon
/ˈprəʊtəɡ(ə)n/Biochemistry. Now historical
noun
A fatty substance, occurring chiefly in the white matter of the brain, consisting of a mixture of cerebrosides and sphingomyelin (originally thought to be a single substance).
Origin
Mid 19th century; earliest use found in Proceedings of the Royal Society of London. From German Protagon from ancient Greek πρωτο- + ἄγον, neuter present participle of ἄγειν to lead.