Tarious forms of nerve-cells-a, multipolar, from gray matter of spinal cord'; b, d, bipolar, from ganglia on peterior roots of spinal nerves; c. g. unipolar, from bellum; g shows indications of a process coming off at www end; 4, union of three multipolar cells in spinal ,, union of three cells in gray matter of brain.

Nerves-c, ordinary-sized nerve-tube, showing axis cylinder surrounded by white substance; d, smaller nerve-tube, with white substance scarcely visible; e, still smaller, with no white substance visible; f. varicose nervetube, from gray matter near surface of brain; a, nervetube, coloured by perosmic acid, showing one of the nodes of Ranvier, or complete interruption of the axis cylinder; b, nerve-tube showing nucleus and node of Ranvier (the axis cylinder is blackened by the action of the per mic acid): 9, non-medullated nerve-tubes from sympathetic, having no white substance, and nucleated at intervals.