ON THE OCCURRENCE AND PHYSIOLOGICAL SIG- 

 NIFIC\\NCE OF FAT IN THE MUSCLE FIBERS 

 OF THE NORMAL MYOCARDIUM AND ATRIO-VEN- 

 TRICULAR SYSTEM: INTERSTITIAL GRANULES 

 (MITOCHONDRIA) AND PHOSPHOLIPINES IN CAR- 

 DIAC MUSCLE 



H. HAYS BULLARD 



From the Anatomical Laboratories, School of Medicine, University of Pittsburgh 



SIXTEEN figures' 



CONTENTS 



Introduction 1 



Methods 4 



Differentiation of neutral fat 5 



Relation of neutral fat to structure of cardiac muscle 7 



Occurrence of neutral fat in the heart muscle of different mammals under 



various nutritive conditions 10 



Physiological significance of neutral fat in cardiac muscle 19 



Occurrence and significance of neutral fat in the muscle tissue of the atrio- 

 ventricular system 21 



Interstitial granules (mitochondria) and phospholipincs in cardiac muscle 24 



Summa ry 28 



INTRODUCTION 



In this paper I shall consider the occurrence and physiological 

 significance of microscopically demonstrable neutral fat in the 

 fibers of normal cardiac muscle and shall also discuss briefly the 

 so-called true interstitial granules and their relation to the 

 phospholipincs of the heart. I have examined more than two 

 hundred apparently normal mammalian hearts. Of these, the 

 one hundred and forty-four last studied are listed below in 

 tabular form. 



Normal cardiac muscle fibers, like other tissues of the body, 

 contain a very considerable percentage of fats. This important 

 fact has been determined by Krehl ('93), Rosenfeld ('01), Leick 



'A large part of the cost of illustrations was borne by the Anatomical 

 Laboratories, University of Pittsburgh. 



1 



TUB AMERICAN JOURNAL OF ANATOMY, VOL. 19, NO. 1 

 JANUARY, 1916 



