84 CAUSE OF THE CARDIAC IMPULSE. 



(3.) The ventricle undergoes during systole a slight spiral twisting 

 on its long axis ("lateralem inclinationem" Harvey), so that the apex 

 is brought from behind more forward, and thus a greater portion of the 

 left ventricle is turned to the front. This rotation is caused by the 

 muscular fibres of the ventricles, which proceed from that part of the 

 fibrous rings between the auricles and ventricles which lies next the 

 anterior thoracic wall. The fibres pass from above obliquely down- 

 wards, and to the left, and also run in part upon the posterior surface 

 of the ventricle. When they contract in the axis of their direction, 

 they tend to raise the apex, and also to bring more of the posterior 

 surface of the heart in relation with the anterior thoracic wall (Harvey, 

 Kiirschner, Wilckens). This rotation is favoured by the slightly spiral 

 arrangement of the aorta and pulmonary artery (Koruitzer). 



These are the most important causes, but minor causes are as 

 follows : 



(4.) The " reaction impulse " is that movement which the ventricles 

 are said to undergo (like an exploded gun or rocket) at the moment 

 when the blood is discharged into the aorta and pulmonary artery, 

 whereby the apex goes in the opposite direction i.e., downwards and 

 slightly outwards (Alderson 1825, Gutbrod, Skoda, Hiffelsheim). 

 Landois, however, has shown that the mass of blood is discharged into 

 the vessels 0'08 of a second after the beginning of the systole, while 

 the cardiac impulse occurs with the first sound. 



(5.) When the blood is discharged into the aorta and pulmonary 

 artery, these vessels are slightly elongated, owing to the increased blood - 

 pressure (Senac). As the heart is suspended from above by these 

 vessels, the apex is pressed slightly downwards and forwards towards 

 the intercostal space (?) 



Guttmann and Jahn observed that the cardiac impulse disappeared after sudden 

 ligature of the aorta and pulmonary artery, while Chauveau and Eosensteiu 

 maintain that it persists. 



As the cardiac impulse is observed in the empty hearts of dead 

 animals, (4) and (5) are certainly of only second-rate importance. Filehne 

 and Pentzoldt maintain that the apex during systole does not move to 

 the left and downwards, as must be the case in (4) and (5), but that it 

 moves upwards and to the right a result corroborated by v. Ziemssen, 

 which, however, is disputed by Losch. 



It is to be remembered that as the apex is always applied to the chest- wall, 

 separated from it merely by the thin margin of the lung, it only presses 

 against the intercostal space during systole (Kiwisch). 



After the apex of the curve, c, has been reached at the end of the 



