A STUDY OF THE INTERCALATED DISCS OF THE 

 HEART OF THE BEEF 



H. E. JORDAN AND J. B. BANKS 



Department of Anatomy, University of Virginia 



FIFTY-ONE FIGURES (fOUR PLATES) 



CONTENTS 



I. Introduction 285 



II. Histologic methods 288 



III. Descriptive 289 



a. The ventricular myocardium 289 



b. The atrial myocardium 298 



c. The moderator band 301 



d. The atrioventricular connecting bundle 303 



e. The fibers of Purkinje 306 



f. The fetal myocardium 308 



IV. Discussion 314 



V. Summary of results 324 



VI. Literature cited 328 



I. INTRODUCTION 



This investigation involves a detailed microscopic study of the 

 fetal and adult myocardium of the beef, including the atrio- 

 ventricular bundle of His, the moderator band, and the fibers of 

 Purkinje. The end in view is to test, in the light of additional 

 data, the four chief hypotheses regarding the significance of the 

 intercalated discs: (1) That they are intercellular cement sub- 

 stance (Schwigger-Seidel,^ Eberth,^ Zimmerman (24), et al.); 

 (2) that they are regions of muscle growth, that is, differentiating 

 sarcomeres (Heidenhain (4) ) ; (3) that they are of the nature of 

 tendons (Marceau (19) ) ; and (4) that they represent local modi- 

 fications of the myofibrils, of the nature of irreversible con- 

 traction phenomena following unusual functional conditions or 



1 For bibliography, and discussion of the early literature, see Jordan (5). 



285 



