22 H. HAYS BULLARD 



considers the true interstitial granules to be of a non-fatty nature. 

 He terms them 'sarcosomes' in order to distinguish them from 

 pathological fat droplets. Knoll ('80, '81, '91) beheves the true 

 interstitial granules of Kolliker to have a fatty marginal layer 

 and a central portion possibly of lecithin. Arnold ('07) thinks 

 that the glycogen of striated muscle is bound to the sarcosomes. 

 He observed that sarcosomes which contain glycogen stain by 

 Best's carmine method ('06) while those that are free from gly- 

 cogen remain colorless. Regaud and Favre ('09) demonstrated 

 granules in the tongue muscles of the rabbit by Regaud's formalin^ 

 bichromate iron-hematoxyUn method. They believed these 

 granules to correspond to Kolliker's granules. Chemically they 

 were thought to be an albumino-lipoid. Bell ('11) finds that the 

 large Q granules of insects contain no fatty substance and are 

 widely different chemically from the interstitial granules of verte- 

 brate muscle. He thinks that the microsomes of Altmann may 

 be artefacts, and is evidently of the opinion that other observers 

 have mistaken fat droplets in vertebrate muscle for the true inter- 

 stitial granules. 



1. Refractive character. Fibers from the pectoralis major of 

 the pigeon or the wing muscles of an insect may be teased and 

 placed, without the addition of fluid, upon a slide, the cover 

 glass being applied with shght pressure. Such preparations show 

 the fat droplets as highly-refractive globules but the true inter- 

 stitial granules seem to have approximately the same refractive 

 index as the substance of the muscle columns and are not clearly 

 visible. However they may be seen as faintly-refractive bodies 

 after normal saline has been drawn under the cover-glass. 



2. Solubility. As has been observed by Kolliker and others 

 the true interstitial granules are disintegrated and partially dis- 

 solved by water. In order to test the effect of fat solvents upon 

 the granules I have examined sections prepared by the paraffin 

 process after fixation in 97 per cent alcohol. In sections from 

 the heart or pectoral muscles of the pigeon, the granules in alcohol 

 fixed material 'are seen as broken fragments. A comparison of 

 these sections with others made after formalin-bichromate fixation 

 shows that a large part of the substance of the granules has dis- 

 appeared from the alcohol fixed material. This suggests the idea 



