THE PLEXIFORM DISTRIBUTION. 



289 



FIG. 86. 



researches, whether the nerve itself receives at its ex- 

 treme ends the vibrations of the waves of light, or 

 whether another part exists, the oscillations of which act 

 upon the optic nerve and produce a peculiar excitation 

 in it. At all events there do ascend from the mem- 

 brana limitans slightly curved fibres (Fig. 85, /), proba- 

 bly connective tissue with its corpuscles, which afford a 

 kind of stay or support to the whole apparatus (support- 

 ing fibres [Stiitzfasern]), and are not, I should suppose, 

 freely connected with the rest of it. 



We have, gentlemen, by the consideration of these re- 

 lations brought out the fact, that the specific energy of 

 individual nerves does not so much depend upon the pe- 

 culiarity of the internal structure of their fibres as such, 

 but that a great deal must be attributed to the special 

 terminal arrangement, with which the nerve is connected, 

 either directly or by contact, and from 

 which the different nerves of sense de- 

 rive their peculiar powers. If for exam- 

 ple we examine a transverse section of 

 the optic nerve external to the eye, it 

 offers no peculiarities as compared with 

 other nerves, which could at all account 

 for this particular nerve's being better 

 able to conduct light than other nerves, 

 whilst on the other hand the peculiar 

 manner in which its extreme ends are 

 distributed sufficiently explains the un- 

 usually great sensitiveness of the retina 

 to light. 



With regard to the terminations of 

 nerves, there is still one mode to be men- 

 tioned ; the plexiform distribution. This 



Fig. 86. Division of a primitive nerve-fibre at , where we find a constriction ; 

 &', b" branches, a. Another fibre, crossing the former one. 300 diameters. 



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