Bauhaus-Universität Weimar

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.
        

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