PES examined microscopically the secretion of the Meibomian glands with various chemical reactions, and he concludes that the chief constituent is cholestrin. This is saponified by the alkaline tears and is washed away. With excessive secretion it remains as a white, foamy mass on the lid margins.
Reference:Arch Ophthalmol. 1898;27:421.
A look at the past . . .. Arch Ophthalmol. 1998;116(12):1662. doi:10.1001/archopht.116.12.1662