298 E. T. Bell, 



tritive plane of the animal ? What is the exact genetic relation (if any) 

 between Kölliker's true interstitial granules and fat droplets? Are 

 s^'milar granules to be found in other tissues than muscle ? What is the 

 ultimate significance of the granules ? Are they stored food substances ? 

 Are they purely metaplasmic substances, or are they cell organs ? Are 

 Altmann's interstitial granules identical with those described by other 

 observers ? 



This paper is presented with the hope that it will partially answer 

 some of the above questions. It is believed that the methods of investiga- 

 tion employed, if adopted by other ober vers, will bring out much more 

 information in regard to the interstitial granules. In order to make a 

 complete presentation of the subject, it has been found necessary to 

 repeat a little from the prehminary paper (Bell, 1910) of which this 

 article is a continuation. 



In this paper the term "interstitial granule" will be employed as a 

 general term to designate any granule, of whatever nature, occurring 

 in the sarcoplasm between the fibrils. Any interstitial granule composed 

 wholly or in part of fatty substances will be called a "liposome". 



Review of the literature^). The interstitial granules of striated muscle 

 were mentioned in 1841 by Henle, who called attention to their insol- 

 ubility in acetic acid. In 1846 Lebert and Robin mentioned fine gran- 

 ules between the fibrillae in the muscle fibers of some invertebrates. 

 The granules were seen by Kolliker in 1850. 



Auhert [1853] figured and gave a brief description of the granules 

 in the thoracic muscles of insects. He states that they are to be seen 

 only in fresh muscle, that they often form regular rows, and that they 

 are not dissolved by acetic acid. 



The first complete description of the granules was given by Kol- 

 liker [1857]. He described and figured clearly rows of granules in frog 

 muscle. The fat droplets in frog mascle come from the pale interstitial 

 granules. As to solubility the granules in frog muscle are not very different 



^) It is not claimed that this review is complete. Some contributions may 

 have been omitted where the titles of the papers were not suggestive of the sub- 

 ject in question. It has not seemed advisable to give all of the literature in 

 connection with some of the secondary topics discussed in this paper. 



