440 THE DYNAMICS OP CARDIAC ACTION. 



gen. The venous blood that reaches it through the Thebesian 

 channels has been depleted of this gas by the rest of the or- 

 ganism, and the suprarenal secretion, owing to its marked avid- 

 ity for it, must, while in transit through the inferior vena 

 cava, have deprived it of the little that might have remained 

 in loose combination. We have reviewed the ultimate distribu- 

 tion of the coronary arteries as given by Berdal. It does not 

 differ from that of other text-books. These generally concur 

 in stating that the larger branches are distributed to the con- 

 nective tissue between the large fasciculi, and once therein 

 divide into arterioles, which, in turn, subdivide into capillaries 

 that entwine the primary muscle-fasciculi. "The capillaries 

 of the myocardium are very numerous," say Bohm and von 

 Davidoff, "and so closely placed around the muscle-bundles that 

 each muscular fiber comes in contact with one or more capil- 

 laries." Do they serve here, as elsewhere, to supply the muscle- 

 fiber with its source of energy i.e., the carbohydrates that enter 

 into the formation of the myosinogen besides furnishing the 

 oxidizing substance which sustains the combustion processes 

 when brought into contact with this myosinogen? This is pre- 

 cisely where a difference between the muscular functions of the 

 heart and those of other muscular structures appears to us to 

 exist. 



There is practically no passive period in the heart's action 

 when we consider that its stage of activity recurs every three- 

 fourths of a second; and the formation of myosinogen in its 

 contractile elements, were it to proceed as slowly as it does else- 

 where, would seem totally inadequate. Still, if the coronary 

 blood is not endowed with the mission of supplying the heart- 

 muscle with its source of energy, we are relegated to the venous 

 blood of the Thebesian vessels and its suprarenal secretion for 

 the myosinogen-forming products. A possible source of en- 

 ergy suggests itself when we consider that a carbohydrate 

 known to react under the effects of the oxidizing substance is 

 present in the hepatic veins, i.e., dextrose, and that this 

 sugar must pass through the right heart. As is well known, 

 these veins carry their sugar to the inferior vena cava. That 

 it is not used by the heart, however, was shown by a careful 

 analysis of the whole question. This is submitted in the twelfth 





