This section is from the book "Materia Medica Pharmacy, Pharmacology And Therapeutics", by W. Hale White. Also available from Amazon: Materia Medica Pharmacy, Pharmacology And Therapeutics..
Amyl colloid is painted on the skin over painful areas in neuralgia, sciatica, etc. It is an elegant method of obtaining the local anaesthetic action of aconitine and veratrine, which is aided by the evaporation of amyl hydride; but it is extremely difficult to make a clear solution. When the collodion has formed a film, a piece of warm, moist spongiopiline helps the anaesthetic effect of the alkaloids.