direction, say to the right. The extent of this pull depends on the amount of contraction. A band of paper or a revolving drum-surface moves at a uniform speed at right angles to the direction of motion of the writing lever. When the muscle recovers from the stimulus, it relaxes into its original form, and the writing point traces the recovery as it moves now to the left, regaining its first position. A curve is thus described, the rising portion of which is due to contraction, and
the falling portion to relaxation or recovery. The ordinate of the n issa the ti response, and the abscissa the time , iMacsaaaue Davies (fig. 1). RECORDER Characteristics of the response- ““)one is securely held at one curve: (1) Period, (2) Amplitude, °%% the other end being con- Under the action of stimu- lus the contracting muscle over the travelling recording ° cle recovers from contrac- may these response-curves be dis- tion, the tracingpointretumns tinguished from each other. Ag on P the record of muscle 5 - curve. regards the period, there is an activity of the muscle. For instance, in tortoise it may be as high as a second, whereas in the wing-muscles of ‘It is probable that a continuous graduated scale might, as suggested by Hermann, be drawn up in the animal curve represents the intensity of The muscle M with the attached nected with the writing lever. (3) Form.—Just as a wave of sound pulls the lever and moves (2) amplitude, and (3) form, SO surface P. When the mus- to its original position. See enormous variation, corresponding to the functional many insects it is as small as z4, part of a second. kingdom, from the excessively rapid contraction of B32
