[Illustration: FIG. 7.--DIAGRAM OF CELLS OF CEREBRAL CORTEX (after Starr, Strong and Leaming). I, superficial layer; a, fusiform; b, triangular; c, polygonal cells of Ramon y Cajal; II, layer of small pyramids; d, smallest; e, small; f, medium-sized pyramidal cells with axones descending to the white matter and giving off collaterals in their course; III, layer of large pyramidal cells; g, largest (giant) pyramidal cells; k, large pyramidal cells with very numerous dendrites; all pyramidal cells are seen to send long apical dendrites up to I; m, Martinotti cell with descending dendrites and ascending axone; n, polygonal cells; IV, deep layer; p, fusiform cell; q, polygonal cell; V, the white matter containing the axones from the pyramidal cells, d, e, f, g, and from a cell of the deep layer q; r, neuroglia fibers. (Barker.)] {114} [Illustration: Fig. 8.--SCHEME OF LOWER MOTOR NEURON. The motor-cell body, with protoplasmic processes, axis cylinder, side fibrils or collaterals, and end ramifications, represents parts of a neuron. a. h., axon hillock devoid of Nissl bodies, showing fibrillation; ax., axon. This process near the cell body becomes surrounded by myelin, m., and a cellular sheath, the neurilemma (not an integral part of the neuron); c, cytoplasm showing Nissl bodies and lighter ground substance; d, protoplasmic processes (dendrites) containing Nissl bodies; n., nucleus; n., nucleolus: n. r., node of Ranvier; s. f., side fibril; n. of n., nucleus of neurilemma; tel., motor end plate or telodendrion; m., striped muscle fiber; s. l., segmentation of Lautermann. (Barker.)]