GRANULES AND FAT OF STRIATED MUSCLE 19 



numerous than in the rabbit, especially in the muscles of the 

 tongue and in the diaphragm. In the powerful and active pec- 

 toralis major of the pigeon and of the bat, the true interstitial 

 granules as demonstrated by the Weigert method are relatively 

 large and occur in great numbers in each fiber (fig. 5). In so 

 far as I have observed, the granules which stain blue with Cresyl- 

 violett, (fig. 7), may be demonstrated in considerable numbers in 

 every striated muscle fiber of all vertebrates. As already men- 

 tioned, granules to be demonstrated by this method do not always 

 correspond with those shown by the Weigert and Altmann 

 methods. 



In cardiac muscle, as pointed out by Kolliker, Knoll and Holm- 

 gren, the granules are especially abundant. I have examined 

 the heart muscle of the dog, the rat and the pigeon. The num- 

 ber and size of the granules is very striking. I have not been 

 able to demonstrate the true interstitial granules in human cardiac 

 or skeletal muscle, due doubtless to the fact that fresh material 

 was not obtainable. 



General occurrence of fat droplets 



Kolliker ('88, '89) describes fat droplets as of general occurrence 

 in muscle fibers of insects and vertebrates. However, he was 

 evidently somewhat in doubt as to their being true fat droplets. 

 He speaks of the droplets as fat like granules or as the long known 

 dark (fat?) granules. Walbaum ('99) examined the muscles of 

 119 human bodies. He found fat droplets in some of the fibers 

 of about two-thirds of the cases examined. Droplets were most 

 numerous in the eye muscles and of very infrequent occurrence 

 in the diaphragm. Ten per cent formalin was used as a fixative. 

 He examined teased preparations in water and in normal saline 

 and observed that many of the fatty droplets are left unstained 

 by Sudan iii. Retzius ('91) beheved that fat droplets are not 

 normally present in muscle fibers. Among others Stadke witch 

 ('94), Ricker and Ellenbeck ('99) and Kemp and Hall ('07), may 

 be mentioned as faihng to find fat droplets in the normal muscle 

 fibers of adult vartebrates. As is well known, the muscle fibers 

 of the winter frog are crowded with fat droplets while such drop- 



