A text-book of physiology . rve. It is essentialthat at starting the point of the marker of thetuning-fork should be exactly underneath the markerof the lever, or rather, since the point of the leveras it moves up and down describes not a straightline but an arc of a circle of which its fulcrum isthe centre and itself (from the fulcrum to the tipof the marker) the radius, that the point of themarker of the tuning-fork should be exactly onthe arc described by the marker of the lever, eitherabove or below it, as may prove most then at starting the tuning-fork marker be thuson the a
A text-book of physiology . rve. It is essentialthat at starting the point of the marker of thetuning-fork should be exactly underneath the markerof the lever, or rather, since the point of the leveras it moves up and down describes not a straightline but an arc of a circle of which its fulcrum isthe centre and itself (from the fulcrum to the tipof the marker) the radius, that the point of themarker of the tuning-fork should be exactly onthe arc described by the marker of the lever, eitherabove or below it, as may prove most then at starting the tuning-fork marker be thuson the arc of the lever marker, and we note on thecurve of the tuning-fork the place where the arcof the lever cuts it at the beginning and at the endof the muscle-curve, as at Fig. 8, we can count thenumber of vibrations of the tuning-fork which havetaken place between the two marks, and so ascer-tain the whole time of the muscle-curve; if forinstance there have been 10 double vibrations, each 12 PENDULUM MYOGRAPH. [Book Fig 11. The Pendulum Myograph. The figure is diagrammatic, the essentials onl}^ of the instrument being smoked glass plate A swings with the pendulum B on carefully adjusted Chap. THE CONTRACTILE TISSUES 73 bearings at C. The contrivances by wliicli the glass plate can be removed andreplaced at pleasure are not shewn. A second glass ])late so arranged that thefirst glass plate may be moved u]) and down without altering the swing of thependulum is also omitted. Before commencing an ex])erimeiit the pendulum israised up (in the figure to the right), and is kept in that positi(jn by the tooth acatching ou the spring-catch /;. On depressing the catch b the glass plate is setfree, swings into the new position indicated by the dotted lines, and is held in thatposition by the tooth a catching on the catch //. In the course of its swing thetooth a coming into contact with tlie jjrojecting steel rod r, ivnocks it on one sideinto the position indicated
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