Experiments on the section of the glossopharyngeal and hypoglossal nerves of the frog, and observations of the alterations produced thereby in the structure of their primitive fibres.

The “law of Wallerian degeneration”. The experiments recorded in the above paper were the starting-point of the neuron theory. Waller showed that if glosso-pharyngeal and hypoglossal nerves are severed, the outer segment, containing the axi cylinders cut off from the cells, undergoes degeneration, the central stump remaining intact for a long period. From this he inferred that nerve cells nourish nerve fibers.