THE MYOCARDIOGRAPH. 



39 



If the pulse frequency vary in the proportion 100 : 270, the duration 

 of systole varies in the proportion 136 : 100. In other words, when the 

 frequency increases, the diastolic period of rest shortens -far more than 

 the systolic period. 



The following observations on animals confirm this conclusion : 



Systole. Diastole. 



Normal duration, 0-149 : 0*373 sec. 

 0-253 : 0'299 ,, 



Systole. Diastole. 



On excitation of vagus, . 0'158 : 0'635 sec. 1 

 ,, ,, accelerator, 0'210 : 0'044 ,, 2 



By Roy and Adami an instrument has been constructed by which the 

 actual contraction of the mammalian heart can be investigated. 3 



In their myocardiograph, one end of the rod (a), as is shown in the 

 figure, can, by means of gimbals, freely oscillate from b. The other end is 

 fastened to a chosen spot on the ventricle. On this rod is fixed a small 

 pulley, over which there passes a 

 silk thread. The one end of this 

 thread is attached by a hook to some 

 other part of the heart, while the 

 other end is connected with a 

 writing lever. By the arrangement 

 shown, the shortening between any 

 two points on the external surface 

 of the heart can be recorded ; and, 

 further, by passing the hook through 

 an auricle and affixing it to a flap 

 of an auriculo-ventricular valve, the 

 movements of the valve and the pull 

 of the papillary muscles can be 

 studied. For the ventricular end of 

 the rod (a), by which the pulley is 

 carried, remains a fixed point, while 

 the hook attached to the thread is 

 in systole approximated to, in diastole 

 driven from, this point. A myo- 

 graphic curve of the ventricle thus 

 obtained can be compared with intra- 

 ventricular pressure curves or aortic FIG. 27. Myocardiograph. a, connecting rod ; 



b, frame with guiding hole for thread ; 



c, hooked needle moving with heart muscle ; 



d, guide for needle ; B, frame viewed from 

 above. Roy and Adami. 



curves recorded synchronously.- 



The cessation of the output is 

 placed by these authors at the 

 moment when the ventricle has 

 reached its maximum of contraction, and according to them the ventricle 

 remains contracted for a certain interval after the cessation of the output. 

 They further consider that the contraction of the papillary muscles pulls 

 down the auriculo-ventricular valves, and, by thus increasing the intraven- 

 tricular tension, causes a temporary arrest in the myocardiographic curve. 

 They find that the apex of the aortic pulse curve corresponds with this 

 moment, and therefore this apex is by Roy and Adami ascribed to the rise 

 of intraventricular tension, produced by the pull of the papillary muscles. 

 The ventricular wall and the papillary muscles remain in contraction for a 

 period which corresponds to the plateau stage in the curve of intraventricular 

 pressure. Reasons have, however, already been given for regarding many of 

 these deductions as incorrect. 



1 v. Frey, "Die Untersuch. des Pulses," Berlin, 1892, S. 86. 



2 Baxter, Arch. f. PhysioL, Leipzig, 1878, S. 132. 



3 Roy anil Adarni, Phil. Trans., London, 1892, vol. clxxxiii. B, p. 207. 



4 Roy and Adami, Practitioner, London, 1890, vol. xliv. p. 414. 



