"The Outgrowth of the Nerve Fiber as a Mode of Protoplasmic Movement" (1910), by Ross Granville Harrison

In ?The Outgrowth of the Nerve Fiber as a Mode of Protoplasmic Movement,? Ross Granville Harrison [4] explores the growth of nerve fibers in vitro [5]. The purpose of this experiment was to test two possible hypotheses for the growth of nerve fibers. Santiago Ramón y Cajal [6] suggested that nerve growth is due to the extension of nerve fibers as they push through tissue. Victor Hensen?s syncytial theory proposed an opposing view of nerve growth. He proposed that each neuron [7] was connected by threads of cytoplasm and the successful connections stimulated further differentiation [8] of the correct neural connections. Using hanging drop tissue cultures, Harrison provided significant evidence for Ramón y Cajal?s theory by showing discrete cell membranes between cells and observing the growth of individual neurons.