At the age of 19, he wrote a report on his work and sent it to philologist Alexander Ellis, a colleague of his father (who would later be portrayed as Professor Henry Higgins in Pygmalion). Ellis immediately wrote back indicating that the experiments were similar to existing work in Germany, and also lent Bell a copy of Hermann von Helmholtz's work, The Sensations of Tone as a Physiological Basis for the Theory of Music.