Action of Carbon Dioxide and Adrenalin on the Heart. 373 



Systemic Output. — Evans and Starling (8) found a constant relation between 

 the flow from the coronary sinus and the total coronary output in the 

 proportion of 3:5; Markwalder and Starling (9) proved that the coronary 

 flow depended on the arterial pressure, and, using the above figure as a 

 basis for calculation, showed that the total output from the left ventricle was 

 constant for a given venous inflow and independent of the arterial resistance 

 within very wide limits. They have confirmed also the observations (10) 

 made previously, that adrenalin causes an increased coronary flow. 



Table I* contains the results of an experiment carried out on the heart-lung 

 preparation in which a Morawitz cannula was introduced into the coronary 

 sinus, and the blood flow through the coronary sinus and that through the 

 systemic part of the schema were measured at the same time. The figures in 

 column 10 (Total coronary circulation) were obtained by multiplying the 

 observed coronary sinus flow by the factor 5/3. It will be seen that in the 

 two series with the normal heart, the coronary output depends on the aortic 

 pressure, while the total output is independent of the arterial resistance 

 within wide limits and is conditioned only by the venous inflow. During 

 the period of administration of carbon dioxide the coronary flow was the 

 same as in the normal condition : but it was increased markedly during the 

 recovery period from carbon dioxide, while the heart was returning to its 

 normal state. This increase was probably due to the accumulation of 

 ' metabolites ' in the heart during the action of CO2. 



Adding adrenalin to the circulating blood caused a great rise in the 

 coronary flow, and this occurred also when adrenalin and carbon dioxide 

 were given together. 



We have thus a guide to the interpretation of the results obtained in other 

 experiments where the systemic output only was measured. 



Systemic or Effective Output with Carbon Dioxide and Adrenalin. 

 Experiments on Boys. — The figures in column 7 of Table I show that the 

 administration of C0 2 may cause a marked falling-off in the output per 

 minute. This diminution may be small with low percentages of C0 2 , but 

 I have never observed an increased output during the administration. The 

 diminution becomes more marked as the percentage of CO2 is increased ; so 

 that if the CO2 is strong, or a moderate percentage is administered for a 



* In this and the other Tables, the following abbreviations are employed : — A.E. = 

 pressure in mm. Hg in air chamber surrounding the thin rubber tube forming the 

 arterial resistance. B.P. = mean arterial pressure in mm. Hgas measured in the cannula 

 in the innominate artery. I.V.C. = pressure in inferior vena cava in mm. H 2 0. V.S. = 

 venous supply. =,+, — = maintained constant, increased or diminished. Systemic 

 output = output in c.c. per 10 sees, as measured on the venous side of the artificial 

 peripheral resistance. 



