Action of Carbon Dioxide and Adrenalin on the Heart. 395 



is accompanied by an increase in the coronary output, so that the total 

 ventricular output is above normal. The slower contraction is also more 

 effective in driving a mass of blood into the aorta instead of firing it out 

 suddenly. 



Cannon (21) has recently summarised the evidence of the significance to 

 the organism of the function of the adrenal medulla in times of great 

 emergency. We have found that the heart muscle is not only better- 

 nourished by increased coronary supply, but the contractile process is also 

 strengthened in a specific manner. "We have probably obtained in the heart- 

 lung schema with maximum venous inflow and proper proportions of CO2 

 and adrenalin, the conditions occurring in short severe muscular exercise, 

 where the muscles of the arms and abdomen are contracted, while the legs 

 are active, all aiding the venous return to the chest, the increased depth of 

 respiration also assisting the venous return. The small excess of CO2 is both 

 the call to the secretion of the adrenals, which dilates the coronary vessels 

 and strengthens the cardiac contraction, and the cause of the lengthened 

 diastole and time for greater filling, so that the maximum output of the 

 heart can be obtained. 



Conclusions. 



1. Carbon dioxide alone depresses all the functions of the isolated heart. 



2. Adrenalin, besides dilating the coronary vessels, has a specific action in 

 increasing the rate and strength of ventricular contraction. 



3. The effect of carbon dioxide and adrenalin combined is still to allow of" 

 more rapid and stronger contraction and rapid relaxation, and also to lengthen 

 the diastolic period. Thus greater filling of the heart takes place and the 

 heart is in a better condition for putting out a maximal output. 



I have much pleasure in recording my thanks to Prof. Piper, of Berlin, for 

 his assistance with the endocardiac pressure tracings, and to Prof. Starling, of 

 London, for the initiation and successful carrying out of the whole work. 



REFERENCES. 



1. Kaya and Starling, ' Journ. Phys.,' vol. 39, p. 347 (1909). 



2. Mathison, ' Journ. Phys.,' vol. 41, p. 416 (1910). 



3. Mathison, 'Journ. Phys.,' vol. 42, p. 283 (1911). 



4. Jerusalem and Starling, 'Journ. Phys.,'' vol. 40, p. 279 (1910). 



5. V. Anrep, 'Journ. Phys.,' vol. 45, p. 307 (1912). 



6. Itami, ' Journ. Phys.,' vol. 45, p. 338 (1912). 



7. Knowlton and Starling, 'Journ. Phys.,' vol. 44, p. 206 (1912). 



8. Evans and Starling, ' Journ. Phys.,' vol. 46, p. 413 (1913). 



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