GRANULES AND FAT OF STRIATED MUSCLE 29 



upon as neutral fat. As already mentioned, Knoll ('80, '81, '90) 

 thought the true interstitial granules to be composed, in part at 

 least, of lecithin, but he too considered the fat droplets to be 

 neutral fat. Bell ('10) holds that neutral fat droplets in muscle 

 fibers are readily stained by simple alcoholic solutions of Scharlach 

 R, but man}'' 'liposomes', which are not so highly refractive as 

 neutral fat droplets and consist wholly or in part of lipoids, can 

 be stained only by alkaline Scharlach R (Herxheimer's method). 

 Bell ('11) thinks the liposoms consist mainly of olein together 

 with some low-melting fat other than olein. He states that many 

 faintly-refractive liposomes which do not stain readily with 

 simple alcoholic solutions of Scharlach R or with osmic acid, 

 are stained somewhat faintly by Herxheimer's method and are 

 composed in part of a substance other than fat, possibly an albu- 

 mino-lipoid. Liposomes which stain faintly by Herxheimer's 

 method and contain a non-fatty element are believed by Bell 

 to be of most common occurrence in the muscle fibers of poorly 

 nourished individuals. 



1. Refractive character: Double refraction. The fatty droplets 

 of muscle fibers may be seen in fresh tissue to which no foreign 

 substance has had access. Preparations are made by rapidly 

 teasing the fibers on a slightly warmed slide and applying a cover 

 glass with slight pressure. The droplets present the highly 

 refractive appearance characterisitic of fat droplets and must be 

 regarded as pre-existing bodies, that is to say they are not produced 

 by histological reagents. Fat droplets are well brought out in 

 fresh preparations mounted in normal saline. They vary some- 

 what in refractive index in different individuals but usually the 

 variation in a single preparation is not pronounced. The true 

 interstitial granules may also be observed in such preparations. 

 These granules likewise vary somewhat in refractive index but 

 are usually less refractive than the fat droplets. Judging merely 

 from refractive index certain granules may be classed as either 

 faintly refractive fat droplets or highly-refractive true interstitial 

 granules. Preparations mounted in 2 to 5 per cent potassium 

 hydroxide show the fat droplets very clearly for an hour or more 

 but the true granules disappear almost immediately. 



