306 E. T. Bell, 



ules not shown by any other fat stain are stained by this method. The 

 granules are nearly all completely dissolved by absolute alcohol and 

 ether. Their solubility and staining reactions seem to afford good 

 evidence that they are all composed wholly or in part of fats. Similar 

 fatty granules may be demonstrated in almost all kinds of cytoplasm, 

 but their number, size, and staining-intensity vary greatly^). 



Material. Muscle samples from a large number of animals have 

 been studied. The animals used to the greatest extent were: rats, 

 frogs, and cats. A considerable number of cattle and dogs have 

 also been studied, as well as the wing muscles of a few moths and flies. 

 Usually only a few muscles from each animal were examined, since 

 variations in the number, size, etc. of the interstitial granules seems 

 always to be uniform thruout the musculature. The muscles usually 

 selected were the gastrocnemius, soleus, extensors of the thigh, psoas, 

 and diaphragm; but other muscles were sometimes examined. The 

 animals studied were on various planes of nutrition. Some were exceed- 

 ingly fat, others were very emaciated. The majority, however, were 

 in ordinary condition. 



Methods. The methods of staining have been fully explained in a 

 previous paper (1910) to which the reader is referred for details. 



a) Fresh tissue. Fresh muscle was teased and examined in the 

 tissue juices, or sometimes a little aqueous humor was added. This 

 method shows all the more refractive granules readily ; but it is usually 

 difficult to see the faintly refractive ones. 



b) Normal salt solution and distilled water. Frozen sections or 

 teased specimens were examined in these fluids. The granules , are 

 shown somewhat more clearly than in the tissue juices. The large 

 Q-granules of insect muscle are readily seen in water or salt solution, 

 tho they are rather faintly-refractive. 



c) Potassium hydroxid. This was used in 1 to 5 per cent solutions. 

 This clears the tissue so that most of the liposomes are very clearly 

 shown. Interstitial granules that do not contain any fats, such as 



*) Some other papers will be reviewed later on in connection with special 

 topics. 



