DISTRIBUTION OF NERVES TO STRIPED MUSCLE. 273 



being soon lost in consequence of their ramification 

 in the deeper layers. 



In the drawing represented in PL XIV, fig. 2, the 

 relation of the nerve-fibre to the finest part of some 

 of the branching muscles of the tongue of the frog 

 is represented; and I have observed an arrange- 

 ment precisely similar in the case of the muscular 

 walls of the lymphatic hearts of the same animal. 

 The very thin and narrow muscular fibres of the 

 heart and tongue would appear to offer very many 

 advantages for the demonstration of ends and end- 

 organs, supposing them to exist ; but the most careful 

 observation under the most favourable circumstances, 

 and with the aid of the highest powers, reveals only 

 delicate nucleated nerve-fibres, forming lax networks, 

 branches of which may often be followed for a very 

 long distance, and then traced into neighbouring 

 nerve-trunks. Some fine branches of nerve-fibres 

 which are in course of development are represented 

 in Fig. 1, pi. XIV. Muscular fibres and connective 

 tissue are seen in the same specimen which is mag- 

 nified 700 diameters. 



289.* The finest nerve-fibres which influence the 

 muscle. The active part of the nerve-fibre, as regards 

 the elementary muscular fibre, commences only at the 

 point where the dark-bordered character of the nerve- 

 fibre ceases, and it therefore follows that the most 

 important and most active portion of the peripheral 

 nerve-fibres distributed to muscle, has escaped the 

 observation of many observers. The fibres are ex- 

 tremely delicate, and, like other very fine nerve-fibres, 

 can only be rendered visible by special methods of 

 preparation. Every nerve-fibre, however fine, is 

 compound, being composed of several fine fibres. 

 " Nuclei " are invariably found in relation with these 

 fibres, and they vary in number in different cases. 



From the foregoing observations I conclude that 

 the nerve-fibres which are to be regarded as the 



s 



