

442 THE DYNAMICS OF CARDIAC ACTION. 



therefore, they are not terminal, is based on the incorrect 

 premise that terminal arteries cannot be thus injected, and 

 has no weight against the positive evidence of the complete 

 failure of nutrition following closure." As we interpret the 

 process, the absence of anastomosis further suggests the exist- 

 ence of an additional source of energy; but the cardiac arrest 

 after ligation of the coronary also indicates that compensation 

 from the opposite heart can only be gradually established. On 

 the whole, the coronaries of the right side are as important 

 as if they alone supplied the needs of the functions of that 

 side. The granules fj and the adrenal secretion are furnished to 

 compensate for the absence of arterial blood in the right auric- 

 ulo-ventricular cavities and in their Thebesian channels; but, 

 the right coronaries being the only source of one of the three 

 necessary factors of the process, their obliteration means as 

 much as that of the left coronaries does to the left heart. 



We can also understand why the contractile elements of 

 the primary fasciculi are bare. They are constantly bathed 

 in the plasma from which they obtain the granules (3 that 

 enter into the formation of their myosinogen. The absence 

 of oxygen in this fluid renders it perfectly harmless to the 

 delicate structures that surround the primary and secondary 

 bundles of muscle-fiber, and to the net-works of arterial capil- 

 laries that hug the bare fibers. The latter, by a rapid absorp- 

 tion, which the presence of sarcolemma would counteract, 

 are constantly forming their products of metabolism: i.e., 

 myosinogen. The arterial capillaries, "coated, on their exter- 

 nal surface, with flat connective-tissue cells" (Berdal), when 

 they cross the spaces of Henle, being the only carriers of oxy- 

 gen, normally become the active factors of nutrition and func- 

 tion. Their blood is the normal excitant as elsewhere. The 

 venous blood brings the granules ?; the adrenal secretion, by 

 contracting the cardiac walls, forces it into the Thebesian chan- 

 nels; the bare muscle-fibers absorb the granules and convert 

 them into their own particular kind of fuel, myosinogen; the 

 capillary blood supplies the energy for this metabolism oxy- 

 gen and simultaneously sustains, again with its oxygen, the 

 combustion processes upon which the continuous work of the 

 organ depends. Here, as elsewhere, the potential energy of 



