220 Construction of Darh or Bouhle-hordered Nerve Fibre. 



these muscular fibres appear, while the granules become more 

 separated from each other. In the embryo of three months, the 

 striation is already quite distinctly seen ; at the same time, the 

 granules appear in the form of minute quadrangles. If we take 

 further into consideration that the electro-motor behaviour of the 

 striated muscular fibres in a state of rest, as well as their changes 

 in a state of activity, are similar to those observed on the nerves, it 

 might be presumed that perhaps, between the terminations of the 

 motor-nerve fibres and these muscular fibres, a more intimate 

 relationship exists than is now supposed. And further, if we 

 consider those so-called sareous elements of Boivman as the elemen- 

 tary bodies or agents through which the contraction of the muscular 

 fibre is effected, we might, judging from the above-mentioned 

 analogy of structure, also look upon those granules, composing the 

 fibiils of the axis cylinders, as the true nervous elements — i. e. those 

 anatomical elements thi'ough which the propagation or transmission 

 of the nervous force takes place. 



The sheath of the axis cylinder manifests itself on those of the 

 larger nerve fibres, as already mentioned, through a fine double 

 contour ; the finest only make an exception. On many of the 

 larger axis cylinders the course of the double contour appears wavy, 

 a phenomenon which presupposes certain dilatations at different 

 places of the sheath, and also a displacement of the granules. 

 Sometimes specimens are met with on which these dilatations 

 extend into regular folds, as in Fig. 21, which, however, may have 

 been produced by a stretching of the sheath during the manipulation. 



It remains for me still to demonstrate the manner in which the 

 fibrils of the fibrillous layer of the nerve-medulla arise fi'om the 

 axis cylinder. Already during the first period of these researches, 

 I devoted a considerable part of my attention to this subject, but 

 without obtaining any definite satisfactory results. Frequently in 

 dissecting carefully with fine-pointed needles very thin sections of 

 spinal marrow under the loupe, I would meet with long naked axis 

 cyhnders projecting from the torn ends of nerve fibres, on which 

 the fibrillous layer of the nerve-medulla was observed to terminate 

 by gradually approaching their surface. But as we very often 

 meet in the same way with peripheral nerve fibres, the axis cylin- 

 ders of which have been for a certain distance entirely denuded of 

 their coverings by the manipulation witli the points of the needles, 

 I regarded the former specimens in the same light, especially when 

 the axis cylinders projecting from the nerve fibres were of no con- 

 siderable length. But the observations of a number of these speci- 

 mens of unusual length, the denuded condition of which could not 

 well be ascribed to the manipulation, induced me finally to regard 

 them as torn axis-cylinder processes of the ganglionic bodies. As 

 regarded the true nature of the mutual connections between the 



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