XXI. On the minute structure and movements of voluntary muscle

Abstract My dear Dr. Todd, In offering to your notice the following account of some researches into the minute structure and movements of voluntary muscle, which I commenced at your suggestion, and in the prosecution of which you have so materially aided me, I am encouraged to hope that some parts of the inquiry may not be altogether uninteresting to the Royal Society, to which the first discoveries in this important branch of physiology by Robert Hooke and the illustrious Leeuwenhoek were communicated, and which also possesses, in its later Transactions, important papers on the same subject. It has long been known that voluntary muscle is susceptible of subdivision into minute threads, which being almost uniform in size, unbranched, and united by means of vascular and cellular parts into bundles of varying bulk, have generally been regarded as constituting the essential proximate anatomical element of the organ. All the best observers, since the time of Leeuwenhoek, have recognised the existence of these threads, but their form and composition have been objects of continual dispute, and in the present day we seem to be as little advanced towards the determination of their real nature as ever. The improvements which have taken place in the construction of microscopes, appear indeed to have only afforded grounds for new differences of opinion, as may be seen by the records of the last few years. In 1837 Mr. Skey, after an elaborate investigation, concluded that these threads were tubes containing a soluble gluten, round which were disposed, in longitudinal sets, still finer filaments, which in their turn were held together by circular bands or striee; and since that period, Dr. Mandl, a microscopical observer in Paris, has described and figured them as bundles of fibrils, held together by a spiral coil of filamentous tissue. A more common opinion is, that these threads are bundles of beaded fibrillæ, whose beads being placed side by side, cause the appearance of transverse lines, a view which was first entertained by Fontana, though his claims to it have been often overlooked. More lately Dr. Schwann and M. Lauth have advocated the same doctrine, especially the former, who has adduced additional arguments in its support.