Directions for classwork in experimental physiology / by Sir Edward Sharpey Schafer.

  • Sharpey-Schäfer, E. A. (Edward Albert), Sir, 1850-1935.
Date:
[between 1915 and 1935?]
Catalogue details

Licence: In copyright

Credit: Directions for classwork in experimental physiology / by Sir Edward Sharpey Schafer. Source: Wellcome Collection.

    51/144 (page 39)
    tion of the finger muscles may be recorded by resting the hand across the myograph plate and tying a thread to the abducted forefinger, the other end of the thread being attached to the short arm of the lever; this is to be heavily weighted or to be held down by a strong elastic band. On adducting the finger the lever is raised, and a curve is described on the moving drum which bears a close resemblance to an incomplete and somewhat irregular tetanus produced by ten or twelve stimulations per second. It must not be concluded that this represents the rate of the successive individual contractions which fuse to form the voluntary Fig. 38.—Experiment to investigate the genesis of tetanus. a, Flat steel spring marked at intervals with the number of vibrations corresponding to certain lengths of the spring; h, mercury cup into and out of which a platinum wire attached to the spring dips. contractions, for it has been shown by photographic records of the capillary electrometer (see p. 61) that in a voluntary contraction there are not less than fifty electrical changes per second, and this probably also represents the number of mechanical changes which succeed one another in a voluntary contraction. The causation of the waves of ten or twelve per second is not fully understood. Another method of obtaining the curve of a voluntary contraction is by the use of a transmission myograph, which consists of two tam- bours connected by india-rubber tubing. The first or receiving tambour (which may be represented by an ordinary Marey’s cardio-