XXVII. On the distribution of nerves to the elementary fibres of striped muscle

Abstract

No branch of minute anatomy has received a larger share of attention than the anatomy of striped muscle, and probably no one point has been more carefully investigated than the distribution of nerve-fibres to this important tissue. Very different conclusions have been arrived at, and the various questions at issue have not yet been determined satisfactorily. For the different views entertained with reference to the mode of termination of nerve-fibres I must refer to the treatises on minute anatomy, and especially to Professor Kölliker’s work just published, where a summary of the results of numerous investigations will be found. Kühne’s Observations . The most recent observations are probably those of Kühne, who states that the nerve-fibre can be traced up to the sarcolemma. He concludes, with some other observers, that in the muscles of insects the axis cylinder of the nerve-fibre penetrates this transparent structure, and is connected with the rows of nuclei which are imbedded in the substance of the muscular fibre and lie amongst the fibrillæ. As will be observed by reference to Kühne’s drawings, these points are very indistinctly, and, if I may so say, diffidently represented. Like Kühne himself, I have quite failed to demonstrate in vertebrate animals the arrangement he described in insects. It may be remarked that nuclei amongst the fibrillæ are very abundant in some fishes and reptiles (especially the frog) whose muscles are sparingly supplied with nerves, while in the muscular fibre of many birds and mammalia which are very abundantly supplied, not a single nucleus can be demonstrated in the interior of the fibre. It seems hardly likely that the relation between the nerves and the contractile elements of the tissue should be closer in these cold-blooded, and comparatively inactive vertebrata, than in birds and mammals. The nuclei amongst the fibrillæ of the muscles of vertebrate animals are clearly not connected with nerves.