Syncytial Theory

The syncytial theory of neural development was proposed by Victor Hensen in 1864 to explain the growth and differentiation of the nervous system. This theory has since been discredited, although it held a significant following at the turn of the twentieth century. Neural development was well studied but poorly understood, so Hensen proposed a simple model of development. The syncytial theory predicted that the nervous system was composed of many neurons with shared cytoplasm. These nerves were thought to be present in the embryo from a very early stage and were selected by the function of the target tissue. There were two competing theories to the syncytial theory. Theodor Schwann and Francis Maitland Balfour proposed the sheath cell theory, which states that nerve fibers were the product of secretions by chains of sheath cells. Santiago Ramón y Cajal and Wilhelm His proposed the outgrowth theory of fiber development for individual neurons. The most substantial evidence against the syncytial theory of neural development was produced by Ross Granville Harrison in his studies of the development of nerve fibers.