Henry Gray (18251861). Anatomy of the Human Body. 1918.
processes are of two kinds: one of them is termed the axis-cylinder process or axon because it becomes the axis-cylinder of a nerve fiber (Figs. 626,627,628). The others are termed the protoplasmic processes or dendrons; they begin to divide and subdivide soon after they emerge from the cell, and finally end in minute twigs and become lost among the other elements of the nervous tissue.
FIG. 624 Various forms of nerve cells. A. Pyramidal cell. B. Small multipolar cell, in which the axon quickly divides into numerous branches. C. Small fusiform cell. D and E. Ganglion cells (E shows T-shaped division of axon). ax. Axon. c. Capsule. (See enlarged image)
FIG. 625 Bipolar nerve cell from the spinal ganglion of the pike. (After Kölliker.) (See enlarged image)
FIG. 626 Motor nerve cell from ventral horn of medulla spinalis of rabbit. The angular and spindle-shaped Nissl bodies are well shown. (After Nissl.) (See enlarged image)
The body of the nerve cell, known as the cyton, consists of a finely fibrillated protoplasmic material, of a reddish or yellowishbrown color, which occasionally presents patches of a deeper tint, caused by the aggregation of pigment granules at one side of the nucleus, as in the substantia nigra and locus cæruleus of the brain. The protoplasm also contains peculiar angular granules, which stain deeply with basic dyes, such as methylene blue; these are known as Nissls granules(Fig. 626). They extend into the dendritic processes but not into the axis-cylinder; the small clear area at the point of exit of the axon in