PATHOLOGICAL VARIATIONS IN THE HEART-BEAT. 107 



scale for the distance covered in each second is given, the individual periods of 

 time can be measured. 



It seems probable, however, that the introduction of the tubes into the heart 

 is not without influence on the regular, undisturbed course of its activity. 



In order to determine the conditions present coincidently with the pressure 

 in the ventricle and in the aorta in the dog, Hiirthle employed his blood-pressure 

 recorders (Fig. 67), which were connected by means of tubes with the interior 

 of the ventricle and of the aorta. A cardiogram was taken at the same time. 

 The vertical lines o, i, 2, 3 indicate conditions identical in time in the three curves. 

 The point o corresponds with the beginning of the ventricular contraction and 

 the first sound of the heart ; while the entrance of the blood into the aorta occurs 

 after an interval, namely at the point i. The points 2 and 3, according to Hiirthle, 

 indicate the closure of the semilunar valves (second sound of the heart). Fred- 

 ericq obtained similar results by means of other experiments. 



One point remains to be cleared up, namely, whether the auricle and the 

 ventricle work in exact alternation, in such a way that the auricle relaxes at the 

 instant when the ventricle begins to contract, or whether the ventricle begins to 



Cardiogram. 



Aorta > 

 Time-Recorder. 



Ventricle 



FIG. 32. Simultaneous Record Showing Cardiogram, the Curve of the Ventricular Pressure and that of the Aortic 

 Pressure, from the Dog. Each division of the time-curve = o.oi second (K. Hiirthle). 



contract while the auricle still remains contracted for a short time, so that for 

 a short period of time at least the entire heart is contracted. Heart-beat curves 

 taken from human subjects appear to show that the ventricular contraction begins 

 as the auricular contraction ends; v. Ziemssen and Ter Gregorianz, who made 

 curves directly from the auricle of the exposed heart of a woman, are likewise 

 in accord with the view that the auricular contraction continues for a time while 

 the ventricles are beginning to contract; and also Heigl, on the strength of a 

 similar observation. 



A. Fick, who believes that the contractions alternate, considers this alternation 

 as a means for maintaining the pressure in the large venous trunks approximately 

 constant. As the auricle relaxes at the instant when the ventricular systole begins, 

 there is no impediment to the flow of venous blood into the auricle; whereas if 

 the auricular contraction were to persist, the blood would be dammed back. As, 

 further, the auricle contracts at the instant of ventricular relaxation, there will 

 be no abnormal pressure in the veins. In this way the pressure within the auricle 

 may remain more uniform and the blood-stream in the ends of the veins more 

 constant. 



PATHOLOGICAL VARIATIONS IN THE HEART-BEAT. 



The position of the heart-beat is altered: (i) By the accumulation of fluid 

 ^serum, pus or blood) or of gases in one pleural cavity. Copious effusions into 

 the pleural cavity, which at the same time compress the lung and force it upward, 

 may displace the heart as far as the right nipple. Effusions into the right pleura 

 cause displacement of the heart to the left. As the right heart is forced 



