336 E. T. Bell, 



pale fibers of the gastrocnemius become loaded with moderately-stain- 

 ing liposomes when the rat is fed a week or more on fat meat. When the 

 liposomes first appear they are very faintly-refractive and small. At 

 this stage they are colored faintly by Herxheimer's stain, but are un- 

 affected by osmic acid. Both in the frog and in the rat they gradually 

 increase in size and in staining-intensity as the animal is fed (figs. 8 

 and 9). There is every indication that in the rat and frog at least (as 

 shown by the feeding experiments) the liposomes take up olein from the 

 fat in the food. Certainly the liposome represents a well-defined focus 

 where fat is deposited; but there is no evidence that this focus is a 

 fuchsinophile granule or any other kind of granule. 



When the liposome first appears it seems to contain a relatively 

 small percentage of fat, since it stains very faintly. It has not been 

 determined what the non-stainable portion consists of. Possibly it is an 

 albumino-lipoid. It seems better to regard the liposomes as foci where 

 fat is deposited than to consider them cell organs. 



Fat content of muscle. It is frequently stated that organs microscop- 

 ically free from fat show a large amount of fat upon chemical analysis. 

 But in the microscopic examination the liposomes have been generally 

 overlooked. There are few if any normal tissues microscopically fat-free. 

 The liposomes therefore account for a large amount of the fat that has 

 been supposed to be microscopically invisible. The following experi- 

 ments were made: a) A large part of the musculature of an adult 

 rat was very carefully separated from all connective tissue fat. 

 It is of course impossible to remove absolutely all the connective 

 tissue fat, but certainly very little was left. The muscles were 

 thoroly ground and mixed. Samples were dried and extracted in 

 absolute ether^). The ether extract amounted to 0.8 per cent of 

 the dry substance. The greater part of the extract consisted of an oil 

 that stained intensely in osmic acid and scarlet red. It was probably 

 mainly triolein. The muscle fibers of this rat contained a relatively 

 small amount of fat. The light fibers showed few or no liposomes 

 and the liposomes in the dark fibers stained with only moderate inten- 



*) The extration was made by Messrs. Moulton and Haigh of the Department 

 of Agricultural Chemistry. 



