270 DISTRIBUTION OF NERVES TO STRIPED MUSCLE. 



one above and one below. These not unfrequently 

 give off branches, just before they pass to the mus- 

 cular bundle, which pursue a longer course, and are 

 distributed to other larger muscular fibres ; and often- 

 times branches pass from one muscular bundle to 

 more distant ones. 



From the above observations it follows that the so- 

 called "nerve- tufts " in the breast muscle of the frog 

 are bodies of a very complex structure. They consist of 

 developing muscular fibres, which are freely supplied 

 with nerves ; and the number and distribution of the 

 nerves render it probable, not only that there are 

 entering and emerging fibres, nerve-loops, and plexuses, 

 or networks, upon the muscular fibres, rather than free 

 ends, but that the action of the new muscular fibres 

 may be harmonized with those of the older elementary 

 muscular fibres of the muscle by branches of nerve 

 fibres which are probably commissural. 



289. Of the arrangement of the nerve-fibres in 

 other forms of striped muscle, as the branching 

 fibres of the tongue, the muscular fibres of the heart, 

 and lymphatic hearts of the frog. To certain forms 

 of striped muscle in which no distinct membranous 

 tube of sarcolemma can be demonstrated, nerves are 

 freely distributed ; but all attempts to demonstrate 

 end-organs or terminal extremities in such textures 

 have hitherto failed. In the heart the existence of 

 delicate nerve-fibres arranged to form networks is 

 distinct; and perhaps the most favourable locality 

 for demonstrating these fibres is the auricle of the 

 frog's heart. Bundles of exceedingly fine nerve- 

 fibres, much resembling those in the bladder, can be 

 seen running in different directions and branching 

 amongst the delicate networks of exceedingly fine 

 muscular fibres. Very fine fibres may be observed in 

 thin specimens with the aid of high powers, crossing 

 the fine muscular fibres at different angles, then 

 dipping down in the intervals between them, and 



