28 H. HAYS BULLARD 



a somewhat pale red. The color in the case of oleic acid appears 

 to be too faint to fully account for the intense red of the true 

 interstitial granules, and thus it is doubtful that these granules 

 contain a pure oleic acid. 



6. Results with Sudan III, osmium tetroxide, gold chloride. 

 Sudan iii does not color the true interstitial granules unless we 

 take into account an extremely faint yellow to be obtained after 

 the action of potassium bichromate. The granules are slightly 

 darkened, but not blackened, by 2 per cent osmic acid follow^ed by 

 pyroligneous acid or by alcohol for reducing the osmium. Retzius 

 ('90), Knoll ('91), and others have stained the true interstitial 

 granules' with gold chloride but the gold precipitate is not con- 

 sidered differential for the presence or absence of fat. 



7. Summarij. The observations presented above are of too 

 general a character to permit of definite conclusions as to the 

 chemical nature of the true interstitial granules of Kolliker. It 

 is certain that the granules contain a non-fatty element, probably 

 of a proteid nature. It may be stated that the substance upon 

 which depends their staining by basic dyes, as well as by the more 

 complex methods of Altmann, Weigert and Regaud, is a substance 

 soluble in fat solvents. In part this soluble substance may be 

 protected from fat solvents by the action of formalin as w^ell as 

 by chrom-osmic mixtures. The solubility and staining reactions 

 of the granules indicates that they may be an albumino-fatty 

 compound or mixture, possibly an albumino-lipoid. There is 

 no reason to suppose that the granules in muscle fibers are funda- 

 mentally different chemically from granules to be demonstrated 

 by similar methods in other tissues of the body. It is reasonable 

 to suppose that the true interstitial granules of muscle fibers are 

 subject to some variation chemically in different species and under 

 varying nutritive conditions. 



h. Chemical nature of fat droplets 



The fat drojjlets of muscle fibers are mentioned by man}'" obser- 

 vers but few have attempted to determine the exact chemical 

 nature of the fat . Usually , it seems, the droplets have been looked 



