24 H. HAYS BULLARD 



it would appear to be of little or no clinical significance. In 

 several of the normal cats listed in tables 4 and 5 the amount 

 of fat in the Purkinje fibers was nearly as large as in this case of 

 pneumonia. 



Differences due to species. In sheep, hogs and oxen the bundle 

 of His is composed of typical Purkinje fibers and these normally 

 contain only a small amount of fat even when the cardiac fibers 

 are crowded with droplets. In cats, dogs and in man, as is 

 well known, the Purkinje fibers are not typical but resemble 

 more closely the ordinary cardiac muscle. In these latter ani- 

 mals the amount of fat in the muscle fibers of the bundle of His 

 varies between wide limits and is often as much or more than is 

 found in the cardiac fibers. In both groups of animals the 

 muscle fibers of the sino-auricular node and the atrio-ventricular 

 node normally contain only a small quantity of fat. 



Physiological significance. From the above observations it is 

 evident that visible fat droplets are normally and almost invari- 

 ably present in the muscle fibers of the His bundle both in the 

 fetus and in adults. It would be going too far to say that fatty 

 droplets in the muscle fibers of the atrio-ventricular system are 

 never of pathological significance. My observations are not suf- 

 ficiently extensive to justify any conclusion regarding the relation 

 between nutrition and fat in the Purkinje fibers. 



INTERSTITIAL GRANULES (MITOCHONDRIA) AND PHOSPHOLIPINES 

 IN CARDIAC MUSCLE 



The phospholipine content (lecithine and related compounds) 

 of cardiac muscle is, I believe, to be found in association with 

 a non-fatty substance in the true interstitial granules of Kol- 

 liker ('89). Knoll ('91) long ago pointed out that these granules 

 swell in water and stain with gold chloride and concluded that 

 they may be composed, in part, of lecithine. 



Figures 15 and 16 show the true interstitial granules in the 

 cardiac muscle fibers of a dog. The sections were stained by Bens- 

 ley's acid-fuchsin toluidin blue method as given by Cowdry ('12). 

 Similar granules were observed in the cardiac fibers of the other 

 animals used in this study. True interstitial granules are known 



