432 THE DYNAMICS OF CARDIAC ACTION. 



the Thebesian foramina of the septum, of at least some arte- 

 rial blood. That this does not always suffice to maintain 

 interventricular equilibrium, however, is illustrated by the 

 dicrotic pulse, the pulsus paradoxus, and other kindred phe- 

 nomena. 



Suggestive in this connection are the remarks of Professor 

 Porter in his review of the subject of cardiac innervation in 

 the "American Text-book of Physiology" 9 : "A positive dem- 

 onstration that the nerve-cells in the heart are not essential 

 to its contractions," says this observer, "is secured by remov- 

 ing the tip of the ventricle of the dog's heart and supplying 

 it with warm defibrinated blood through a cannula tied into 

 its nutrient artery. Long-continued, rhythmical, spontaneous 

 contractions are thus obtained (Porter 10 ). As the part removed 

 contains no nerve-cells, the observed contractions can only 

 arise in the muscular tissue, provided we make the (at present) 

 safe assumption that the nerve-fibers do not originate im- 

 pulses capable of inducing rhythmic muscular contractions." 

 As will be shown, the cardiac nerve-fibers, as in all the organs 

 we have reviewed, merely impose upon the muscular fiber the 

 required vibratory rhythm. This is well illustrated by the fol- 

 lowing experiment: If the apex of a frog's heart "is suspended 

 in normal solution," says the same author, "and a constant 

 electric current kept passing through it, beats will appear 

 after a time, the frequency of pulsation increasing with the 

 strength of the current" (Langendorff 11 ). But Porter also re- 

 marks, almost prophetically in the light of our views: "The 

 demonstration that the nerve-cells are not essential to con- 

 traction places us one step nearer the true cause of contrac- 

 tion. It is some agency acting on the contractile substance. 12 

 Evidence is accumulating that this agent is a chemical substance, 

 or substances, brought to the contractile matter by the blood." 



That the "chemical substance brought to the contractile 

 matter by the blood" is represented by the adrenal secretion 

 and the oxidizing substance seems clear. 



Porter: "American Text-book of Physiology," second edition, 1900. 



10 Porter: Journal of Experimental Medicine, vol. ii, p. 391, 1897. 



11 Langendorff: Archiv fur gesammte Physiol., Ixi, p. 336, 1895. 

 13 All italics are our own. 



