Fig. 13.—Myograph, an instrument for recording the contraction of a muscle. A, wooden stand; B, vertical brass pillar; C, sliding forceps or clamp for holding upper end of femur of nerve-muscle preparation; D D, short vertical pillars, on the top of which the lever E E works; F, scale-pan for weight; J, marker; G, glass plate; K, counterpoise to keep J in contact with G; H, counterpoise to lever E E. The nerve-muscle preparation is covered with a glass shade, to the walls of which pieces of wet blotting-paper are attached, thus forming a moist chamber to keep the nerve from drying.