Experimental physiology.

  • Sharpey-Schäfer, E. A. (Edward Albert), Sir, 1850-1935.
Date:
1912
Catalogue details

Licence: In copyright

Credit: Experimental physiology. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    FATIGUE OP MUSCLE AND NERVE Effects of fatigue on muscle: (a) On the form of the muscle curve.— Take a nerve-muscle preparation and fit it up as for recording the simple muscle curve (p. 27). Make an abscissa, and mark, as usual, upon it the point of stimulation. Take a normal curve with the muscle free-weighted. Remove the writing point from the drum, which is then allowed to revolve continuously and to stimulate the muscle with each revolution. After fifty of such excitations without record, apply the lever point again to the drum (making use, of course, of the stop), and let the muscle describe another curve at the same place as the first. Remove the writing point again for the duration of fifty excitations, and repeat the above procedure, and so on a number of times until the fatigue curves are pronounced. Notice the effects of fatigue upon muscle, in prolonging the latency period, diminishing the amount and slowing the course of its con- traction, and greatly delaying, and at length even preventing, its relaxation. A fatigue curve or series of curves can also be obtained by allowing the lever point to remain in contact with the cylinder during the whole of the experiment, and thus recording every contraction ; but the individual curves in a tracing so obtained are very numerous, and tend to obscure one another. (6) On the extent of contraction.—The effect of fatigue upon the extent of contraction is best recorded upon a stationary drum, moved by hand about half a millimeter after each excitation, or on a very slowly moving drum; the extent of the contraction is shown by the ordinates described by the lever. Use the slowest rate of move- ment of the drum (1 mm. per second or less), and arrange the primary circuit so that it is made and broken about every half-second. This can be done either by closing and opening a key by the hand, or by allowing a metallic bridge, actuated mechanically {e.g. by a