. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. 186 ANIMAL PHYSIOLOGY. The Changes in a Muscle during Conteaction. Though the change in form is very great during the con- traction of a muscle, the change in bulk is almost inappreci- able, amounting to a diminution of not more than about tsV? of the volume. In fact, according to the latest investigator, there is no diminution whatever. A series of levers may be laid on a muscle or the columns of air in a series of Marey's tambours may be influenc
. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. 186 ANIMAL PHYSIOLOGY. The Changes in a Muscle during Conteaction. Though the change in form is very great during the con- traction of a muscle, the change in bulk is almost inappreci- able, amounting to a diminution of not more than about tsV? of the volume. In fact, according to the latest investigator, there is no diminution whatever. A series of levers may be laid on a muscle or the columns of air in a series of Marey's tambours may be influenced by the contracting muscle, and from some such apparatus a graphic record like that seen in Fig. 183 may be obtained. It is to be observed that the contraction passes along the muscle in the form of a wave, the size and speed of which are. FiQ. 183.—Tracing of the propagation o£ the muscular wave. Chronographic tracing, one hundred vibrations per second underneath (Marey). susceptible of measurement. For the frog the wave-length is estimated at from 200 to 400 mm., and the velocity at about 3 to 4 metres per second. It is probably rather greater in the muscles of mammals and greater under the more natural conditions of the muscle in the intact living body. But since the fibers of striped muscle are of very limited length (30 to 40 mm.), it would seem that a contraction origi- nating in one fiber must be capable of initiating a similar action in its neighbor; and, as the ends of the fibers lie in con- tact, it is easy to understand how the wave of contraction spreads. Normally, the contraction must pass from about the center of the muscle-cell where the nerve terminates in the end-plate. The microscopic changes occurring in contracting muscle are not well understood. The living muscle of a beetle's thigh when placed under a microscope may be seen in contraction—a sight of the most striking nature, reminding one of a billowy, tempestuous sea, and by the use of reagents the
Size: 3568px × 700px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthormillswes, bookcentury1800, bookdecade1880, bookyear1889
