Action of Carbon Dioxide and Adrenalin on the Heart. 387" 



time the systole of the ventricle is slower, and the next auricular systole 

 shows as a well marked interruption of the diastolic part. 



Endocardiac Pressure. — The curves were obtained in Berlin on the heart- 

 lung preparation by means of the small manometers designed by Piper (15) 

 according to F rank's specifications, and recording photographically. Figs. 7 and 

 10(1) show the effect on the form of the intraventricular pressure curve of 



Fig. 7.- — Effect of 12 per cent. C0 2 on Left Auricle and Ventricle. Read from l ight to 

 left. Experiment 3, a, Table VI. 



(a) Normal, T. 34% B.P. 102, I.V.C. 12, O.P. 101 c.c. in 10 sees. 



(b) 12 per cent. C0 2 , T. 34% B.P. 102, I.V.C. 30, O.P. ? 



small percentages of CO2 in the air breathed : the isometric period is not 

 so steep as in the normal curve, the ventricle taking a longer time to 

 develop the same amount of pressure (see Table VI, 1, 2, 3, 5, 8). The 

 total length of systole is longer, and relaxation is slower ; but it is a delay 

 of the whole process of the heart cycle, and the proportion of systole to 

 diastole remains about the same as in the normal beat. The maximum 

 pressure exerted by the ventricle is usually a little less, 108 mm. Hg, as 

 against 117 mm. in the normal, with the same venous supply and same 

 arterial resistance (Table VI, Experiment 3). 



After adrenalin the ventricle more rapidly reaches a certain tension in the 

 isometric period,* and relaxation is also rapid ; but the total diastolic time is 

 proportionally longer than normal. For instance, in Experiments 6 and 7, 

 Table VI, the diastole represented 52 per cent, of the total heart cycle, 



light reflected from a mirror, we found the interruption due to auricular systole well 

 marked, even with full venous supply after adrenalin. 



* Wiggers(16) has already noted this in the right ventriule. 



