26 H. HAYS BULLARD 



poorly stained shrunken fragments, having evidently suffered a 

 loss of substance. This shows that the granules contain a non- 

 fatty substance together with a substance soluble in fat solvents 

 but rendered insoluble by the action of potassium bichromate. 

 The shrinkage of the granules in absolute alcohol is evidently 

 not due to dehydration for the substance which is removed from 

 them is stained by basic dyes, and is rendered insoluble by po- 

 tassium bichromate. This makes it certain that the substance 

 removed by alcohol is not aqueous but fatty. 



From the above observations we may conclude that the true 

 interstitial granules of cardiac fibers are made up of at least two 

 substances, one fatty the other non-fatty. The properties of 

 the fatty component indicate that it can not be neutral fat but 

 may very well be a phospholipine. Remembering that neutral 

 fats and phospholipines together are known to constitute practi- 

 cally the entire fat content of cardiac muscle, the fatty sub- 

 stance of the granules, since it does not correspond to the former 

 must be the latter — phospholipine. We have, moreover, already 

 accounted for the neutral fat in the form of droplets which stain 

 with Herxheimer's Scharlach R. 



The conclusions just drawn are in full accord with the chemical 

 findings of Krehl ('93) and Rubow ('04-'05) who have shown by 

 analyses that the phospholipine content of heart muscle is re- 

 markably uniform, being well-nigh constant even in inanition. 

 The neutral fat, on the other hand, fluctuates in amount. The 

 true interstitial granules under all conditions yet observed are 

 surprisingly uniform and not subject to any definite variation 

 even in inanition while the quantity of Scharlach R. fat is vari- 

 able. Erlandsen ('07) demonstrated that cardiac muscle contains 

 more than twice the quantity of phospholipine that is present in 

 skeletal muscle. We again find that the true interstitial granules 

 are, on the average, more than twice as abundant in cardiac as 

 in skeletal muscle. Those who are familiar with the staining 

 reactions and microchemical properties of mitochondria are no 

 doubt aware that the properties of the granules, as given above, 

 indicate that the latter structures are in fact mitochondria as was 

 stated by Regaud ('09). 



