STRUCTURE AND ARRANGEMENT OF THE NERVE ELEMENTS. 623 



an observation obviously gives material support to the view that the nerve-fiber 

 is a chain of individual cells. 



In the spinal nerves those fibers are the thickest that are the longest to their 



FIG. 220. i, Primitive fibrils; 2, axis-cylinder; 3, fibers of Remak; 4, meduUated varicose fibers; 5, 6, medul- 

 lated fibers, with sheath of Schwann; c, neurilemma; t t, the annular constrictions of Ranvier; b, the medul- 

 lary substance; d, cells of the endoneurium: a, axis-cylinder; x, medullary drop or myelin-globule; 7, trans- 

 verse section of a nerve with distinct axis-cylinders, medullary sheaths and endoneurium; 8, nerve-fiber treated 

 with silver nitrate; the axis-cylinder striated transversely (after Frommann). I, Multipolar ganglion-cell of 

 the spinal cord; z, neurite; y, dendrites; to the right a bipolar ganglion-cell. II, Peripheral sympathetic 

 ganglion-cell with connective-tissue capsule. Ill, Ganglion-cell with surrounding fibers; m, capsule; n, 

 cellulifugal, o, cellulipetal fiber. 



end-organ; and those ganglion-cells are the largest that give off the longest 

 nerves. 



According to Ewald and W. Kiihne both the axis-cylinder and the medullary 

 sheath are further surrounded by an exceedingly delicate horny sheath consisting 

 of neurokeratin. Both are connected through the substance of the myelin by 



