68 



THE CONTRACTILE TISSUES. 

 FIG. 20. 



The Pendulum Myograph : The figure is diagrammatic, the essentials only of the instrument 

 being shown. The smoked glass plate A swings with the pendulum B on carefully adjusted 

 bearings at C. The contrivances by which the glass plate can be removed and replaced at 

 pleasure are not shown. A second glass plate so arranged that the first glass plate may be 

 moved up and down without altering the swing of the pendulum is also omitted. Before com- 

 mencing an experiment the pendulum is raised up (in the figure to the right), and is kept in that 

 position by the tooth a catching on the spring-catch b. On depressing the catch b the glass plate 

 is set free, swings into the new position indicated by the dotted lines, and is held in that posi- 

 tion by the tooth a' catching on the catch b'. In the course of its swing the tooth a' coming in 

 contact with the projecting steel rod c, knocks it on one side into the position indicated by the 



