CHAP, iv.] METABOLIC PROCESSES OF THE BODY. 719 



456. Before we attempt to discuss further how food and 

 other circumstances thus affect the glycogen in the liver, it will 

 be desirable to take up the matter which we left on one side in 

 449, viz. the consideration of the histological changes occurring 

 in the hepatic cells, under various conditions. It will be con- 

 venient to begin with the cells of the more distinctly tubular 

 gland of the frog. 



In a frog which has not been subjected to any special treat- 

 ment the cell-substance of the hepatic cell (cf. Fig. 92 A) will 

 generally be found to contain lodged in itself three kinds of 

 material, the presence of which, if not directly recognisable in 

 the fresh cell, may be demonstrated by the use of various reagents. 

 In the first place, oil globules of variable size and in variable 

 amount are scattered throughout the cell ; sometimes, as we have 

 already said, these are extremely abundant ; but there is otherwise 

 nothing very special about these fat globules in the hepatic cell to 

 demand any discussion concerning them apart from the general 

 discussion on the formation of fat, into which we shall enter later 

 on. 



In the second place, a number of small discrete granules may be 

 seen lodged in the cell-substance. These appear to be of a proteid 

 nature and are generally most abundant .on the inner side of the 

 cell near the lumen of the bile passage. The presence of these 

 granules is closely dependent on the activity of the digestive 

 processes. They diminish when digestion is going on and accu- 

 mulate again afterwards. Putting aside certain details we may 

 say that these granules behave very much like the granules in an 

 albuminous salivary cell, a pancreatic cell or a chief gastric cell ; 

 and we may probably safely conclude that they, like the granules 

 in these cells, are in some way concerned in the formation of the 

 secretion ; that is, in their case, bile. 



In the third place, the cell contains more especially in its outer 

 parts nearer the blood vessel, away from the lumen of the bile 

 passage, a variable quantity of material which differs from the 

 ordinary cell-substance in being hyaline and refractive and hence 

 glassy looking, and in staining port- wine red with iodine instead of 

 brownish yellow as does ordinary cell- substance. This material is, 

 though with some little difficulty, soluble in water, and by this 

 means may be dissolved out from the cell. When this is done the 

 places which it occupied appear as vacuoles or gaps of various 

 sizes limited by bars of the cell-substance, which thus takes on the 

 form of a network, the meshes of which are wider and more con- 

 spicuous in the outer part of the cell, in which the hyaline 

 material was previously most abundant. In the inner part of the 

 cell where the hyaline material was scanty the cell-substance is 

 mote dense, and even in the outer part a shell of more dense, less 

 reticulate cell-substance affords a definite outline to the cell. 

 There can be no doubt that this hyaline material is either actual 



