Report on the progress of human anatomy and physiology in the year 1843-4 / [Sir James Paget].

  • James Paget
Date:
1845
Catalogue details

Licence: Public Domain Mark

Credit: Report on the progress of human anatomy and physiology in the year 1843-4 / [Sir James Paget]. Source: Wellcome Collection.

    12/66 (page 12)
    the fibrils, whether contracted or relaxed ; the occasional appearance of unmarked fibrils protruding from the end of a torn fibre ; and the frequency of uniform cylin¬ drical filaments in muscle which has been long macerated. And his arguments for the zig-zag condition, or the undulation, to which he ascribes the appearance of transverse striae, on the more or less contracted fibrils, are the following : 1. When the primitive fibres of the muscles recently taken from dying insects contract under w ater, the transverse striae, which at first were wide apart, are ap¬ proximated ; and in every such contraction, the clear as well as the dark transverse lines become narrower, the elevations at the margin of the fibre become more prominent, and the constrictions between them become deeper and narrower. This could not happen if the contraction depended on the formation and widening with flattening of beads, or varicose enlargements of the filaments; for, in this case, the shadows (dark transverse lines), thrown by the beads or enlarged parts, should become broader and more intense as the beads become larger; whereas, in increasing contraction they become more intense and narrower, as the zig-zag angles become more acute 2. The longitudinal striae separating primitive filaments, remain straight even when the filaments are most contracted; whereas if the filaments become beaded, these lines should indicate that form, in the same manner as it is seen at the edge of the fibre where side views of the zig-zag filaments are obtained. 3. In repeated observations of the muscles of crabs, some of which were partial! v dried, and others macerated in water, it was found that, in the former, the indi¬ vidual filaments which projected from the torn ends of fibres were, at their ex¬ tremities, bordered by two perfectly straight lines, which, as they were traced down towards the mass of the fibre, became slightly undulated, then zig-zag in obtuse angles, and then in more and more acute angles, till they could not be recognized as continuous lines. In the macerated muscles, on the contrary, there was scarcelv any trace of transverse stria?, and the filaments appeared in almost every part bounded by straight lines. 4. The appearance of transverse striae, and of rows of spheres may be imitated by thin cylinders of white w;ax, or a similar substance, moulded in undulations or zig-zag flexures, and examined through a tube as they are held against the light, the angles next the observer appearing darker and broader than those next the light; and the same appearance is produced by the coarsely-undulated surface of many muscles and tendinous tissues. [This last argument is of little weight; and the facts stated in the first and secondare just as well explained by supposing, not that the fibrils present a series of varicose bead-like enlargements,but that they are formed by a series of discs, the lines of union of which make the dark transverse striae; or, as Mr Erasmus Wilson* has better ex¬ pressed it, by a linear series of minute cells, flattened at their apposed surfaces, and so compressed longitudinally as to leave no indentation on the surface, thus constitut¬ ing a uniform cylinder divided by transverse septa, which are formed by the adherent surfaces of contiguous cells. Will’s third argument deserves attention ; but as the observations were made on dried and macerated fibrils, no conclusion can be safelv drawn till they are confirmed by observations on muscles in the natural state.] Valentin,f who has long described the relaxed muscular fibril as a uniform cylinder, confirms, generally, Will’s account, though he cannot determine whether the striated appearance ot the fibrils is due to their becoming varicose, or to zig-zag flexures, induced by contraction. He also still holds to his belief | • Report of the Royal Society, Philos. Magazine, Aug. 1844. What I have quoted from the description expresses almost exactly what has appeared, to me to be the structure of the muscular fibril, especially in the large fibres of the eel; except that I doubt greatly whether the component portions of the fibril can be truly called cells; they have, rather, the appearance of solid transparent particles. Neither have I ever seen anything to indicate a varying density of the contents in each successive set of four cells such as Mr. Wilson describes: perhaps this appearance was due to the fibres or fibrils being thrown into the coarse zig-zag flexures, described by some as produced in full contrac¬ tion of the muscle. t Lehrbuch der Physiologie des Menschen, Bd. ii, p. 33 + See Report for 1842, p. 30.