THE SINO- VENTRICULAR BUNDLE: 

 A FUNCTIONAL INTERPRETATION OF MORPHOLOGICAL FINDINGS, 



BY ROBERT RETZEK. 



INTRODUCTION. 



In spite of the large amount of scientific work that has been done on the sub- 

 ject, the problem of how the contraction wave passes from the venous to the arterial 

 end of the heart still remains unsolved. When a muscular connection between 

 atria and ventricles was discovered and it was found that the severance of this 

 connection brought about arhythmia, many adherents of the myogenic theory 

 felt that the burden of proof lay with the neurogenists. It was, however, not long 

 before it was established that there were nerve fibers accompanying this muscular 

 connection and the problem stood as it did before the discoveries of His and Kent. 

 I have devoted the last fifteen years to anatomical studies bearing on this subject 

 and during this time my views have undergone considerable change.* In the 

 present papers I have undertaken to outline the possible interpretations of the 

 facts as we now know them. 



It seems that there is a lack of understanding between the anatomist and the 

 physiologist, because neither seems to appreciate the value of the facts described 

 by the other. For instance, it should not be left out of account that the heart of 

 Limulus (which is unquestionably neurogenic) has more resemblance to voluntary 

 than to cardiac musculature, considering its morphology. Again, the peculiarity 

 of the histologic structure of the muscular connection between the atria and ven- 

 tricles and of the Purkinje fibers is left almost entirely out of consideration by those 

 who hold that the myogenic theory is the only correct one. It is this phase of the 

 question which is the subject of this paper. 



The literature has been so thoroughly reviewed recently by others that 

 I propose to discuss only those articles that have a direct bearing no the sub- 

 ject at hand. The term "atrio-ventricular bundle" was given by His, jr. (1893) 

 to a strand of cardiac muscle which arises in the posterior wall of the right 

 atrium, near the atrial septum, is superimposed on the superior edge of the ven- 

 tricular septum with numerous interchange of fibers, and (passing forward) divides 

 near the aorta into a right and left branch, the latter ending in the aortic leaflet of 

 the mitral valve. It was later found that this bundle does not begin nor end in the 

 manner described by His, but that the region of origin represents the primitive sinus 

 region of the heart, and that it terminates in a complex network of fibers long 

 known as "Purkinje fibers." Imbued with the idea that this connection conducts 

 impulses from atria to ventricles, Tawara (1906) gave it the name of "Reizleitungs- 



*Although a large part of this work was done during my association with Professor Mall, I should like also to record 

 my indebtedness to Professor Keibel of Freiburg, and Professor Felix, of Zurich, for the courtesies extended to me while a 

 guest in their laboratories; and to Professor Bensley for his kindly interest during my residence in Chicago. 



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