40 H. HAYS BULLARD 



latent period, substance from the granules was thought to pass 

 into the muscle columns there to be used in the stage of active 

 contraction. The examination of insect and vertebrate muscle 

 fibers, by the various methods employed in this study, has afforded 

 little in support of Holmgren's views concerning the physiologi- 

 cal significance of the granules. 



Knoll ('80) and Knoll and Hauer ('92) found that the true 

 interstitial granules are not removed in inanition. Feeding 

 experiments with a dozen white rats lead me to conclude that the 

 alcohol-soluble portion of the true interstitial granules which 

 stains with Cresylviolett is increased in amount when rats are 

 heavily fed and decreased when the animals are kept on low 

 rations. This may indicate that the alcohol-soluble substance 

 is of metabolic importance and such an assumption would seem 

 the reasonable one. 



Before dismissing the subject of the physiological significance 

 of true interstitial granules, it should be mentioned that Arnold 

 ('09) believes that glycogen is bound to the sarcosomes (true 

 interstitial granules), and- Kingsbury ('12) thinks that mitochon- 

 dria, in general, act as a reducing agent and in certain cases may 

 be concerned in exercising the function of cell respiration. 



Physiological significance of fat droplets 



The presence of fat droplets in striated muscle fibers has been 

 regarded by Van Gehuchten ('89) and others, as of pathological 

 significance. Probably this is still the prevailing opinion with 

 respect to cardiac muscle. Schaeffer ('93) believed that fat drop- 

 lets in the skeletal muscle fibers of vertebrates may occur under 

 normal conditions but are usually pathological. Walbaum ('99) 

 found that fat droplets were of very frequent occurrence in normal 

 human muscle fibers but thought the quantity of fat bore no 

 direct relation to the nutritive condition of the individual. Kol- 

 liker ('88) regarded the fat droplets of insect muscle as reserve 

 food material. Knoll and Hauer ('92) found that fat droplets 

 in the muscle fibers of pigeons are removed by starvation but the 

 true interstitial granules are not removed. Krause ('11) states 

 that the fat droplets in muscle fibers are not independent of the 



