274 DIAMETER OF FINEST NEKVE-FIBEES OF MUSCLE. 



fibres of distribution are far more delicate and much 

 finer than has been hitherto supposed. The remarks 

 which I make on this head with reference to the 

 ultimate nerve-fibres distributed to voluntary muscle, 

 will apply to the ultimate nerve-fibres distributed to 

 other organs. 



In mammalia the ultimate fibres appear as narrow, 

 long, slightly granular, and scarcely visible bands 

 with oval masses of bioplasm, situated at short but 

 varying intervals, as described in my paper published 

 in the Phil. Trans, for 1860. In many reptiles (frog, 

 newt, lizard, snake, chameleon), however, these ulti- 

 mate nerve-fibres are narrower but much firmer than 

 in mammalia; and they are more readily demon- 

 strated, as they do not give way under the influence 

 of considerable pressure and stretching. Although 

 fine nerve-fibres have been described in certain 

 situations before I drew attention to these fine pale 

 nucleated fibres in muscle, it was not generally sup- 

 posed that the active peripheral portion of nerves ex- 

 hibited these characters ; nor indeed has this fact 

 yet received the assent of many distinguished anato- 

 mists. The arrangement of the fine nerve-fibres in 

 the summit of the papillae of the frog's tongue, 

 described in my last paper presented to the Royal 

 Society (Phil. Trans. June, 1864), and in the mucous 

 membrane of the human epiglottis, will, I venture to 

 think, tend to convince many that the really active 

 peripheral portion of the nervous system consists of 

 excessively fine nucleated nerve-fibres arranged as a 

 plexiform network [1865]. 



29O. Diameter of the finest nerve-fibres of muscle. 

 With reference to the diameter of these finest 

 branches of the nerve-fibres, many can be demon- 

 strated and followed for long distances which are 

 less than the T o-oWo tn f an i nc ^ in diameter ; and 

 there is reason to think that fibres much finer than 

 this actually exist, and serve as efficient conductors 



