1865.] Nerves in Involuntary Muscle. 237 



are crossed sometimes in two or three places by very fine nerve-fibres ; and 

 not unfrequently the nerve-fibre runs parallel with the muscular fibre-cell 

 for some distance. 



These nerve-fibres are extremely fine, and require very high powers for 

 their demonstration. They are certainly not connected in any way either 

 with the nucleus or with the contractile tissue of the muscular fibre. They 

 cross the fibre either obliquely or at right angles ; and oftentimes a nerve-fibre 

 runs for some distance parallel with the muscular fibre. The influence, 

 therefore, exerted by the nerve-fibre cannot depend upon any continuity of 

 texture between it and the contractile tissue, but is doubtless due to the 

 passage of a current through the nerve, which determines a temporary alter- 

 ation in the relations to one another of the particles of which the contrac- 

 tile tissue consists. 



Although I speak of the ultimate nerve-fibres as being arranged so as 

 to form a network, it must not be supposed that this network is arranged 

 on the principle of a capillary network. Every fibre of this network is com- 

 pound ; so that perhaps the term " plexus " more truly describes the ar- 

 rangement. " Plexiform network," I think, expresses the character of the 

 arrangement still more exactly*. 



Some have said that my view accords with the old idea of looplike ter- 

 minations of nerves ; and this is in the main true, but the course of one single 

 fibre forming the loop is far more extensive than was supposed by the older 

 observers, and the " looped fibres " divide and subdivide into finer fibres. 

 This diagram is intended to represent a plan of the arrangement which is 

 shown to exist in many tissues according to my observation. 



Although it be admitted that networks are formed, it might be said that 

 from them fine fibres may branch off here and there, and terminate in ends 

 within the space or area. The results of actual observation and a careful 

 consideration of the various facts bearing upon the question are, however, 

 strongly opposed to such a doctrine. 



Distribution of nerves to the muscular fibres in the walls of arteries, 

 veins, the intestine, ducts of glands, fyc. 



So far as I can ascertain, all involuntary muscular fibre is freely supplied 

 with nerve-fibres, and in all cases the nerves are arranged so as to form 

 networks. In many instances ganglia are seen in connexion with the 

 nerves ramifying amongst the muscular fibre-cells encircling the vessels. 

 I have seen such upon the vessels of all the viscera and those of the palate 



* " In using the term network, I do not mean to imply that fine nerve-fibres unite with 

 each other after the manner of capillaries, but merely that the bundles of fibres are 

 arranged like networks. The fibres composing the bundles do not anastomose. In lace 

 the appearance of a network of fibres is produced ; but every apparent thread is com- 

 posed of several, each of which pursues a complicated course, and forms but a very small 

 portion of the boundary of any one single space. In Plate XLI. fig. 5, a nervous network 

 exists ; but each cord is compound, and composed of numerous fibres which never 

 anastomose." Note appended to a paper in the Phil. Trans. 1862. 



T2 



