FAT AND MITOCHONDRIA IN CARDIAC MUSCLE 7 



RELATION OF NEUTRAL FAT TO STRUCTURE OF CARDIAC MUSCLE 



Position of fat in muscle fibers. Virchow ('47) pointed out that 

 the pathological fat droplets of cardiac muscle fibers are situ- 

 ated in the sarcoplasm, not in the fibrillae or muscle columns. 

 This view has been confirmed by nearly all subsequent observers. 

 Welch ('88) observed that the droplets are arranged in rows be- 

 tween the fibrillae and according to Wegelin ('13) transverse rows 

 are found in segment J on either side of the membrane of Krause. 



In well stained preparations of normal cardiac muscle, made 

 by the Herxheimer method, it is very clearly seen that the fat 

 droplets are found in the sarcoplasm, never in the muscle columns 

 or myo-fibrillae. The. droplets are arranged in both longitudinal 

 and transverse rows, figure 5. When the muscle fiber is con- 

 tracted the larger droplets, about 2 ^i in diameter, are spherical 

 and each occupies an entire segment of the fiber extending be- 

 tween adjacent Krause's membranes. When the fiber is extended 

 the large droplets are usualh^ somewhat elongated and are found 

 in the anisotropic segment Q. Small droplets, 1 ju or less in diam- 

 eter, are arranged in transverse rows in the isotropic segment 

 J on either side of Krause's membrane. 



Light and dark fibers. As regards distribution of affected 

 fibers, Ribbert ('97) recognized three types of fatty degeneration : 



1) diffuse general degeneration in which all the fibers contain fat; 



2) mottled peri-arterial degeneration affecting areas immediately 

 surrounding the smaller arteries; 3) mottled degeneration oc- 

 curring in areas most distant from the smaller arteries. This 

 latter type gives the well known tiger-lily or thrush-breast 

 appearance usually most marked in the papillary muscles. 



In normal cardiac muscle the fatty fibers do not give rise to the 

 mottled appearance but conform closely to the diffuse general 

 type of Ribbert. All of the fibers of a specimen and of the whole 

 heart may show a uniform amount of fat, figure 1, and figure 6 at 

 C. In an equal number of individuals certain of the fibers con- 

 tain much more fat than others, figures 3, 4, 5, 9, 10, and 13. 

 This latter distribution of the fat droplets, at times observed in 

 all the species (rat, cat, dog, hog, sheep, ox, man) here studied, is 



