Amacrine cell ( Cajal, 1899-1904 ) : A neuron (Waldeyer, 1891) characterized by amacrine extensions. They were discovered in the retina (Herophilus, 335-263 BC), in the olfactory bulb (Weitbrecht, 1744), and in the peripheral nervous system (Meckel, 1817) where they are called interstitial cells; they were regarded as having no axon (K├Âlliker, 1896), and thus "amacrine" (see Cajal, 1899-1904). Examples of neurons with amacrine extensions and/or axon, and/or dendrites (His, 1889) are now known; they are very common in nerve nets.