Huber-DeWitt, Nerve-Endings in Muscles. 187 



may however sometimes be spread out over a proportionately- 

 larger area, see Fig. 20, and especially the upper cell of this 

 figure. Sometimes it may be seen the terminal fibrils supply 

 more than one heart muscle cell; this is indicated in Fig. 16, 

 where the fiber sends off a small branch, ending on the cell 

 shown, the fiber itself going on. In this way a fibril of the 

 intra-muscular plexus may innervate four or five successive cells. 

 Figs. 19 and 20 also show this ending of such fibrils on more 

 than one cell. That the endings here described are on the heart 

 muscle cell may be seen in Fig. 21, showing cross sections of 

 heart muscle cells through the nerve ending. 



We have not been able to associate these several types of 

 endings with nerve fibers showing any peculiar or characteristic 

 structure. Wherever it was possible to trace the fibril termin- 

 ating in any one of the above described endings for some dis- 

 tance away from the cell on which it terminated, such a fibril 

 or fiber always presented the appearance of a non-medullated, 

 more or less varicose nerve fiber, the latter characteristic — 

 the varicosity of the fiber — although very constant for non- 

 medullated fibers, not being looked upon as showing any inher- 

 ent structural diiTerences. We are reminded here of what 

 Dogiel has said of. the structure of the ultimate branches of 

 nerve fibers. He describes these as consisting of one or sev- 

 eral ultimate fibrillae, which stain deeply in methylene blue, 

 surrounded by an interfibrillar substance, which stains only 

 faintly in the blue ; then follows this statement : " Letztere (in- 

 terfibrillar substance) lagert sich in iiberlebendem Nerven- 

 gewebe als eine gleichmassig, diinne Schicht an der Peripherie 

 aller Nervenastchen und Faden ab, wahrend sie mit dem Eintritt 

 der postmortalen Veranderungen wahrscheinlich ein wenig auf- 

 quillt und in abgesonderten Kliimpchen sich ansammelt, welche 

 sich auf dem Verlauf der genannten Aestchen vertheilen und 

 ihnen ein charakteristisches Bild geben." If this be so, the dif- 

 erence in the degree of varicosity would depend largely on the 

 rapidity with which such terminal fibers are fixed after the re- 

 moval of the '* ilberlebend" tissue. 



