2l6 



NERVOUS SYSTEM. 



[sect. I 10. 



solubility in acetic acid. The conclusion which may be drawn from these facts 

 appears to me to be simply this, that the axis-cylinder is not an artificial pro- 

 duct, but must be admitted to be an essential constituent of the living nerves. 



Non-medullary nerve-fibres are found in many places. I reckon among 

 them, i. the pale fibres of the Pacinian bodies ; 2. the nucleated pale fibres 

 at the terminations of the olfactory nerves ; 3. the perfectly transparent non- 

 nucleated nerve-fibres in the cornea ; 4. the pale, branched, and in part anas- 

 tomosing nerve-terminations in the electric organs of Torpedo and Baya ; 

 5. the similarly conditioned nerve-terminations in the skin of the mouse 

 (Kolliker), and shrew-mouse (Hessling) ; 6. the pale processes of the nerve- 

 cells of the central organs and ganglia, although they may not all pass into 

 dark-bordered fibres ; 7. the optic fibres in the retina and Mutter's Jibres in 

 the latter, the nerve-terminations in the cochlea ; 8. the nerve-fibres of inver- 

 tebrata and of some fishes. 



§ 1 10. The nerve-cells (nerve-corpuscles, Valentin) (fig. 92), are 

 nucleated cells, which exist iu large numbers in the grey or coloured 



Fig. 92. 



Ct/ 



A 



X 



Nerve-cells, from the acoustic nerve; magnified 350 times. 1. Nerve-cell, with the origin of 

 a fibre, from the anastomosis between the facial and auditory nerves, in the meat. aud. int. of 

 the ox; a. membrane of the cell; 6. contents; c. pigment; d. nucleus; e. continuation of the 

 sheath upon the nerve-fibre ;/. nerve-fibre. 2. Two nerve-cells with fibres, from the nerv. 

 ampull. infer, of the ox; a. sheath with nuclei; b. membrane of the cells; d. a fibre arising 

 from the cell with nucleated sheath. I owe these drawings to the kindness of the Marquis 

 Corti. 



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

 in the nervous trunks and the peripheral expansions of the nerves 

 (retina, cochlea, vestibule). The nerve-cells possess, as outer 

 covering, a delicate, structureless membrane, which can be readily 

 demonstrated in the cells of the ganglia (the ganglion-cells, 

 ganglion-corpuscles), but with great difficulty in those of the 

 central organs; still even here, on the addition of re-agents, the 

 membrane may be seen with tolerable distinctness in the larger 

 cells, whilst in the smallest, just as in the finest nerve-tubes, such 

 a membrane, although it perhaps exists, cannot be distinguished. 



