82 



THE CARDIOGRAM. 



Fig. 25. 



Curves taken from the apex-beat A, normal curve from mau ; B, from a dog; 

 C, vei y rapid curve from a dog ; D and E, normal curves from a mau, regis- 

 tered on a vibrating glass-plate where eacli indentation = O'OIGIS sees. In 

 all the curves, a, //, means contraction of the auricles ; b, c, ventricular 

 systole ; </, closure of the aortic valves ; e, closure of the pulmonary artery 

 valves; e,f, relaxation or diastole of the ventricle. 



elevations are perhaps caused by the contractions of the ends of the 

 veins, the auricular appendices, and the atria themselves. 



.Some observers ascribe the small elevations occurring before b to the rilling of 

 the ventricle during the diastole, whereby it is pressed against the intercostal 

 space (Maurer, Griitzner). 



The portion, l>, c, which communicates the greatest impulse to the 

 instrument, and also to one's hand when it is placed on the apex- 

 beat, is caused by the contraction of the ventricle, and during it the first 

 sound of the heart occurs. Frequently, but erroneously, the cardiac 

 impulse has been ascribed to this contraction of the ventricle. It 

 however, is due to all those conditions which cause an elevation in the 

 region of the apex -beat. 



