GRANULES AND FAT OF STRIATED MUSCLE 17 



In cardiac muscle (pigeon, dog, rat) the true interstitial granules 

 are present in very striking numbers. They are usually confined 

 to the segment Q and correspond to Holmgren's Q granules. 

 Regaud ('09) described and figured the granules in the cardiac 

 muscle of the dog as plate-like structures, confined to segment 

 Q and extending radially between the muscle columns from the 

 periphery of the fiber toward the central sarcoplasmic column. 

 I have examined the cardiac muscle of several dogs and find the 

 true interstitial granules as described by Regaud. 



In the wing muscle fibers of insects the granules are very similar 

 in form and position to either the granules of the pectoral muscle 

 the pigeon and the bat or to those of cardiac muscle in verte- 

 brates. The wing muscle fibers of the Belostoma Americana 

 show rounded granules in transverse section similar to those of 

 the pigeon. The fibers of dragon flies have granules of a plate- 

 like form similar to those of the cardiac muscle of the dog. I have 

 not examined fibers from the leg muscles of insects. 



Retzius ('09) believed that the interstitial granules are united 

 and held in position by a fibrous network, which he demonstrated 

 with gold chloride. A comparison of gold chloride preparations 

 with others made by the various methods already mentioned, 

 leads me to believe that the appearance of a net work uniting the 

 interstitial granules is to be interpreted as a precipitate of gold. 



The position assumed by the granules appears to be determined 

 solely by their size and the pressure of the muscle columns. Per- 

 haps also the position of both the true interstitial granules and 

 fat droplets may be taken as affording evidence in support of the 

 now commonly accepted view that the membranes of Krause are 

 present in the sarcoplasm between the muscle columns. The 

 dumb-bell and diplosomic granules may be formed by a thicken- 

 ing of the muscle columns at Hensen's line. After fixation, and 

 due to the process required for embedding, the substance of the 

 column shrinks leaving its impress upon the granules. The plate- 

 like forms occur in types of muscle that present a radial arrange- 

 ment of the muscle columns. The substance of the granule 

 occupies the space between the columns and thus, in transverse 

 sections, appears in the form of a plate. 



THB AMERICAN JOURNAL OP ANATOMY, VOL. 14, NO. 1 



