2 11. HAYS BU LLAKD 



The granules to be found between the myo-fibrils or muscle 

 columns of cross striated muscle, although mentioned by Henle 

 ('41) were first described in detail by K()lliker ('57) who called 

 them interstitial granules.' He applied the term to both fat 

 droplets and true interstitial granules, the latter being of a non- 

 fatty nature. This paper presents observations concerning the 

 structure of striated muscle with especial reference to interstitial 

 granules and fat droplets, including also a brief discussion of 

 their general occurrence, chemical nature, and physiological 

 significance. A number of important communications dealing 

 with the interstitial granules have included a somewhat compre- 

 hensive review of the literature, namely, Retzius ('90), Arnold 

 ('09), Holmgren ('10), Prenant ('11), and Bell ('11). As several 

 of these papers are of recent date I have thought best to omit a 

 chronological review and shall discuss the literature only in so 

 far as its subject matter has a direct bearing on the topics treated 

 in this paper. 



According to Kolliker both fat droplets and true interstitial 

 granules are of wide distribution, occurring in vertebrate muscle 

 and also in insect muscle. A few observers have denied the exist- 

 ence of two general types of interstitial granides, especially in 

 vertebrate muscle, but usually the work of Kolhker has been con- 

 firmed in this respect. My observations are in accord with those 

 of Kolliker and I shall Ukewise designate the types of granules 

 as true interstitial granules and fat granules or fat droplets. 



For the present it may be said that true interstitial granules, 

 at least for the most part, are not completely soluble in absolute 

 alcohol and not readily stained by fat stains such as Scharlach 

 R, while the fat droplets are easily soluble in absolute alcohol 

 and take the fat stains. This does not necessarily mean that the 

 true interstitial granules contain no fatty substance nor that the 

 fat droplets are composed wholly of fatty substances. Under 

 normal physiological conditions the muscle fibers of both skeletal 

 muscle and cardiac muscle of vertebrates may, and usually do, 

 contain true interstitial granules as well as fat droplets. 



