The microscope and its revelations / by William B. Carpenter.

  • Carpenter, William Benjamin, 1813-1885.
Date:
1868
Catalogue details

Licence: Public Domain Mark

Credit: The microscope and its revelations / by William B. Carpenter. Source: Wellcome Collection.

    804/882 (page 726)
    of this tissue as consisting of ‘ fibres,’ yet the ultimate structure of the ‘ Muscular Fibre ’ is very different from that of the Simple , Fibrous tissues already described. When we examine an ordinary Muscle (or piece of ‘flesh’) with the naked eye, we observe that i it is made-up of a number of fasciculi or bundles of fibres, which are arranged side-by-side with great regularity in the direction in which the muscle is to act, and are united by Areolar tissue. These Fasciculi may be separated into smaller parts, w'hich appear like simple fibres; but when these are examined by the Micro- scope, they are found to be themselves fasciculi, composed of minuter fibres bound together by delicate filaments of Connective tissue. By carefully separating these, we may obtain the ultimate Muscular Fibre. This fibre exists under two forms, the Siriated and the Non-striated. The former is chiefly distinguished by the transversely-striated appearance which it presents (Fig. 387), and which is due to an alternation of light and dark spaces along its whole extent; the breadth and distance of these strife vary, however, in different fibres, and even in different parts of the same fibre, according to its state of contraction or relaxation. Longitudinal striae are also frequently visible, which are due to a partial separation be- tween the component fibrilhe into which the fibre may be broken up.—When a fibre of this kind is more closely examined, it is seen to consist of a delicate tubular sheath, quite distinct on the one hand from the Connective tissue which binds the fibres into fasciculi, and equally distinct from the in- ternal substance of the fibre. This mem- branous tube, which has been termed the Sarcolemma, is not perforated either by Fasciculus of Striated Capillary vessels or by Nerves; and forms, ing at a the transverse 111 fact> a complete barrier between the real strife, and at b its junc- elements of Muscular structure and the tion with the Tendon, surrounding parts. The diameter of the Fibres varies greatly in different kinds of Yertebrated animals. Its average is greater in Reptiles and Fishes than in Birds and Mammals, and its extremes also are wider; thus its dimensions vary in the Frog from l-100th to l-1000th of an inch, and in the Skate from 1-65th to 1 -300th; ; whilst in the Human subject the average is about 1-400th of an | inch, and the extremes about l-200th and l-600th. 568. The elements of Muscular Fibre appear to be very minute cylindrical particles with flattened faces of nearly uniform size, adherent to each other both longitudinally and laterally. The former adhesion is usually the most powerful ; and causes the Fig. 387