A MYOCARDIOGRAPH FOR THE MAMMALIAN HEART. By ARTHUR R. CUSHNY. The myocardiograph which I have used for a number of years to record the movements of the mammalian heart is a modification of the one devised by Roy and Adami, and, like it, is designed to record the changes in the distance between two points on the heart’s surface, while any other move¬ ments do not affect it. For this purpose two points on the surface of the heart are attached to the ends B and L of the apparatus (Fig. 1), and contraction of the fibres between these points causes an approximation of L to B and a corresponding withdrawal of K from C. A light thread attached to K and passing over the pulley is thus drawn upon and pulls down the writing lever, which is arranged to record on smoked paper. AB is a light magnalium rod suspended from a horizontal bar by means of a gimbal joint at A and pierced at B to admit of the attachment of a fine thread. The point B can move freely in the plane perpendicular to AB, but as a matter of fact, its movements are very limited when it is attached to the heart. AB passes through a thin tube CD, which fits it accurately and is interrupted in the middle to admit of a collar E ; this is unattached to CD but is fixed on the rod AB by a screw and thus supports CD at a definite height while permitting it to rotate about three-fourths of its circumference round AB. The upper part of CD bears a small vulcanite pulley over which a thread is run. From the lower half of CD, in the earlier forms of the apparatus, there projected a bar DH ending in axes on which a light lever LK was pivoted. In the newer form the length of this bar can be altered by sliding it into a sheath ; during an experiment its length is fixed by means of a set screw. The bar ends in two axes which carry a short piece of tubing forming a sheath in which the magnalium rod KL can be moved up and down for adjustment to the heart ; after the attachment to the heart is made, this movement is prevented by a set screw, and the rod KL can only move in the axes on which the sheath is pivoted. At L the rod is pierced for attach¬ ment to the heart, and at K for the thread to the writing lever*. To adjust the apparatus to the heart a large number of changes may be made, but these are seldom necessary. Thus KL may be pushed up or down in the sheath, when it is necessary to have L at a higher or lower level than B. * I have sometimes substituted for the pulley and vertical string a tambour attached to C D, the string from K pulling on the membrane ; the movement is then transmitted to a recording tambour in the usual way. Heart. Vol. II, Ko. 1.