72 CELL DIFFERENTIATION AND THE ELEMENTARY TISSUES 



dendrites or protoplasmic processes, and the axone or axis-cylinder process, 

 which forms what is known as a nerve fiber. 



The protoplasm of the cells is shown by various dyes to consist of neuro- 

 fibrils, perifibrillar substance, and in most cells chromophilic bodies. Apathy 

 and others have demonstrated that a network of interlacing and anasto- 

 mosing fibrils traverses both the cell body and its branches, figure 95. 



FIG. 97. An Isolated Sympathetic Ganglion Cell of Man, Showing Sheath with Nucleated Cell 

 Lining, B. A, Ganglion cell, with nucleus and nucleolus; C, branched process or dendrite, D, 

 unbranched process or axone. (Key and Retzius.) X 75- 



The perifibrillar substance is a fluid or semifluid substance in which the 

 fibrils are embedded. By treating nerve-cells with special stains granular 

 bodies of varying size are found embedded in the cytoplasm. These bodies 

 are the chromophilic bodies, figure 96. 



Ganglion cells are generally enclosed in a transparent membranous 

 capsule similar in appearance to the external nucleated sheath of nerve - 

 fibers; within this capsule is a layer of small flattened cells. 



Nerve Terminations. 



Nerve fibers terminate peripherally in four different ways; i, by the ter- 

 minal subdivisions which pass in between epithelial cells, and are known 

 as inter-epithelial arborizations; 2, by motor-plates which lie in the muscles; 

 3, by special end-organs, connected with the senses of sight, hearing, smell, 

 and taste; and, 4, by various forms of tactile corpuscles. 



The Inter-epithelial Arborizations. This forms a most common 

 mode of termination of the sensory nerves of the body. The nerve fibers 



