NERVES OF ORGANIC MUSCLE. 



sometimes elongated, and at others round or rhomboidal. The 

 vessels themselves present no important peculiarities. 



NERVES. In all organs or parts of organs, in the composition 

 of which the organic muscular tissue plays an important role, and 

 apart from differences occurring in particular instances, a similar 

 arrangement of the nerves is to be found. The different nerve 

 fibres contain a variable number of dark-edged and pale nerve 

 tubules. Of these, the former present the features character- 

 istic of the medullated fibres, vary in size, and are usually the 

 most abundant. There are, however, a few fasciculi, which 

 chiefly consist of the pale fibres, and contain but a small number 

 of the dark-edged variety. The former appear as fine glistening 

 filaments, of from 0*0018 to 0*0023 millimeters in breadth, with 

 here and there a nuclear enlargement of 0*003 to 0*005 milli- 

 meters in diameter, a peculiarity which at once enables them to 

 be distinguished from even the finest doubly contoured fibre. 

 The fasciculi thus composed of pale and dark-edged fibres, lie 

 in the connective tissue surrounding the muscle bands or mem- 

 branes, and form wide-meshed flat plexuses, in which the ad- 

 joining fibres cross and interchange from one plexiform layer 

 into another. In the plexus formed by the larger nerves (prin- 

 cipal or fundamental plexus) ganglion cells lie scattered, which 

 are often collected into microscopic ganglia; and from the same 

 plexus fibres are given off, which are at first dark edged, but 

 subsequently assume the form of broad pale bands. These pre- 

 sent a fine longitudinal striation, with nuclei at various dis- 

 tances, which are sometimes smaller than the fibres, and at 

 others cause their edges to project. The pale fibres are from 

 0*004 to 0*005 millimeters in breadth, and their nuclei have 

 about the same diameter. After running for a certain distance 

 they rapidly dimmish in size, and split into finer glistening 

 fibres, which have nuclear enlargements and a diameter of from 

 0*0018 to 0*0023 millimeters, and are similar to those contained 

 in the fasciculi. These fibres form plexuses with meshes of 

 moderate size, and of rhomboidal or elongated shape. Bodies 

 resembling nerve cells or nuclei with distinct nucleoli occupy 

 the points of junction. Pale fibres, proceeding directly from 

 the main or fundamental plexus, enter into this plexus. The 



