File:Kirkes' handbook of physiology (1907) (14746897856).jpg

Identifier: kirkeshandbookof00kirk (find matches)
Title: Kirkes' handbook of physiology
Year: 1907 (1900s)
Authors: Kirkes, William Senhouse, 1823-1864 Greene, Charles Wilson, 1866-1947
Subjects: Physiology
Publisher: New York, W. Wood and company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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ort copper-wire hooks. Lay the nerve across apair of platinum electrodes, shake a little water on the sides of the cover ofthe moist chamber, and place it over the preparation so as to prevent drying ofthe nerve and of the muscle. Arrange an induction coil with its keys, battery, THE SIMPLE MUSCLE CONTRACTION 495 and electrodes connected as shown in the diagram, figure 351. Set the second-ary coil at a position which will give a strong contraction of the muscle, andrecord this contraction on the smoked paper of an ordinary recording cylinder.Whenever the induction shock is sent through the nerve there will be a singlecontraction of the muscle. If this contraction is recorded on the drum stand-ing still, then the record will be a vertical line, the height of which can bemeasured. From it and the arms of the lever the exact shortening of the musclecan be computed. Repeat the stimulus with weaker and weaker currents,until no contraction is produced. As the stimulus becomes weaker a point
Text Appearing After Image:
Fig. 351.—Arrangement of Apparatus in the Induction Coil, as Shown for Single Inductions. is reached at which the contractions rapidly decrease in height and ceasealtogether. If, on the other hand, the stimulus is stronger the contractionsonly slightly increase. Arrange the apparatus so as to stimulate the muscle by an automatic keyattached to the recording drum. Adjust the apparatus and lever and revolvethe drum at a rapid rate, allowing the automatic key to be opened while thedrum is turning at a rapid speed. Or take a record on the pendulum myo-graph, which is especially constructed for this experiment, figure 352. Themuscle contraction now is recorded as a wave which shows some consider-able duration in time. Repeat the experiment, introducing a 100 doublevibration tuning fork to record the speed of the drum, and taking care tomark the exact point on the record where the automatic key is opened. Inthis record the muscle contraction shows three different periods or phases.The fir

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