FIGURE 3. Diagram of the sensory and motor nervous system of a worm (composite of two figures, one from Retzius and another by v. Lenhossék). (A) Sensory cells of the skin; (B) ipsilateral motor cells of central ganglia; (C) crossed motor cells; (D) ipsilateral longitudinal motor cells; (E) multipolar motor cell; (G) terminal ramifications of motor neurons in muscles; (I) interganglionar association cells. Taken from Cajal (1899–1904).