338 E. T. Bell, 



Summary. 



All the interstitial granules of vertebrate striated muscle that are 

 visible in the fresh tissue consist entirely or in part of fatty sub- 

 stances, as is shown by their solubility and staining properties. They are 

 called liposomes. Fuchsinophile interstitial granules are not liposomes. 



The liposomes may be best shown by staining the fresh tissues 

 with Herxheimer's scarlet red. 



In nearly all muscles some of the fibers (dark, or cloudy) contain a 

 relatively large amount of sarcoplasm, and coarse liposomes; others 

 (pale, or light) contain relatively little sarcoplasm, and small liposomes, 

 if any. These are not distinct types since numerous intermediate fibers 

 are present. The dark fibers of the ox have not as much sarcoplasm as 

 those of the cat or frog. When the liposomes are removed (as in inanition) 

 there are no striking differences between the fibers. After feeding with 

 fats the pale fibers may become so filled with liposomes that they 

 resemble the dark fibers of an animal under ordinary feeding. Since the 

 dark fibers contain more sarcoplasm than the light fibers, they are better 

 adapted for the storage of fat. 



Some liposomes are strongly-refractive, others are faintly-refrac- 

 tive ; and numerous intermediate forms occur. The staining-intensity of 

 a liposome is in proportion to its refractive power. The less refractive 

 liposomes probably contain a smaller percentage of fatty substances 

 than those that are more strongly-refractive. 



The liposomes are apparently entirely dissolved by absolute alcohol 

 and ether. 



Fats that are solid at ordinary temperature probably do not form 

 any part of the stainable substance in the liposomes, tho such fats may 

 be present in small quantity. 



Osmic acid stains some liposomes black, others various shades 

 of brown; but a great many are not stained at all. Probably the lipo- 

 somes colored black consist mainly of olein ; those colored brown, of a 

 little olein mixed with some low-melting fat that does not reduce 

 osmic acid. Those that do not reduce osmic acid at all consist of some 

 low-melting fat other than olein. 



