THE NERVOUS SYSTEM. 



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comprehending more than an axis-fibre, still in all probability 

 are capable pretty nearly of assuming its nature.] 



§ 



111 



The nerve-cells, (accessory corpuscles (Belegungskorper), 

 nerve-corpuscles, Valentin), (fig. 140), are nucleated cells, 

 occurring in great numbers in the grey or coloured substance 

 of the central organs, in the ganglia, and occasionally also in 

 the trunks, and peripheral expansions of the nerves [retina, 

 cochlea, vestibule). The nerve-cells are covered externally 

 by a delicate, structureless membrane, which in the cells 

 of the ganglia (ganglion-cells, -globules, -corpuscles), may 

 be demonstrated easily, but with great difficulty in those of the 



Fig. 1 10. 



central organs; the application of re-agents, however, will 

 suffice to show, pretty distinctly, that the membrane exists 

 around the larger cells, even in these situations, whilst in the 

 smallest, just as in the finest nerve-fibres, no membrane has 



Fig. 140. Nerve-cells, x 350 diani., from the acoustic nerve : 1, nerve-cells with 

 the origin of a fibre, from the anastomosis between the facial and auditory nerves, in 

 the meatus audit, int. of the Ox; a, membrane of the cell ; b, contents ; c, pigment ; 

 d, nucleus ; e, continuation of the sheath upon the nerve-fibre ; /, nerve-fibre : 2, two 

 nerve-cells with fibres, from the n. ampult. infer, of the Ox ; a, sheath with nuclei ; 

 b, membrane of the cell ; c, nucleus ; d, the origin of a fibre with nucleated sheath : 

 3, isolated contents of a nerve-cell, with nucleus and two nucleoli. For these draw- 

 ings I am indebted to Dr. Corti. 



