Victor Horsley, John Marshall, nerve stretching, and the nervi nervorum

In his early professional life, Victor Horsley was registrar and assistant to Mr. John Marshall, anatomist, surgeon, and president of the Royal College of Surgeons. In helping with the research for the Bradshaw Lecture on Nerve Stretching given by Marshall in 1883, Horsley demonstrated changes in nerve fibers due to mechanical stretching of the sciatic nerve, and he also demonstrated small nerve fibers in the sheaths of peripheral nerves--the so-called nervi nervorum. Marshall attributed the benefits of nerve stretching in sciatica to the interference with these nervi nervorum hitherto considered to exist only in the sheath of the optic nerve.