304 E. T. Bell, 



Prenant [1904] states that there is no doubt that a large number of 

 the interstitial granules, and in certain cases all of them, are of a fatty- 

 nature ; but these fatty granules are certainly only a secondary condi- 

 tion. The true interstitial granules have not the reactions of fat. They 

 are corpuscles sui generis distinct from fat, and characteristic of the 

 muscle cell. By their reactions they resemble a lecithin. In every case 

 they are a chemical substance preparatory to fat^). 



Kemp and Hall [1907] did not find any fat in the muscle fibers of 

 fattened beef cattle. Keinath [1904], however, found fat in the pectoral 

 muscle fibers of a fattened ox. He examined only one adult animal. 

 These results as well as my own earlier observations [1909] were appar- 

 ently made on fixed material with weak stains, hence the liposomes 

 were not shown. 



Holmgren [1907 — 1910] devotes considerable attention to the inter- 

 stitial granules, particularly to those of insect muscle. The granules 

 may be well shown in tissues fixed in osmic-bichromate and other 

 osmic mixtures; but after fixation in Carney's fluid (alcohol, chloroform, 

 and acetic acid), they can be shown only in contracted fibers and not 

 so well even there. In the wing muscles of insects and in the heart muscle 

 of crustaceans and mammals, the granules correspond in position to the 

 anisotropic segment (Q-granules); but in the skeletal muscles of insects 

 and in general also in those of mammals, the granules correspond in 

 position to the isotropic segment (J-granules) [1910, S. 306]. The fat 

 droplets (stainable by osmic acid) in the wing muscles of insects tend 

 to lie near Krause's membrane. They are secondary metabolic products 

 of the Q-granules. The entire Q-granule is not changed into fat except 

 in special cases (Coleoptera in winter [1910, S, 282]. The appearance 

 of the interstitial granules depends upon the phase of activity of the 

 fiber. They undergo marked changes as the fiber passes from contrac- 

 tion thru the resting stage back to contraction again. Stained prepara- 

 tions of fibers in the "facultative" stage (the stage Just preceding con- 

 traction) show the granules large and pale and the fibrillae deeply 

 stained. At the beginning of contraction the granules fade out but 



^) This is mainly a review by Prenant, and it is not clear to what extent 

 it represents his own belief. 



