442 THE METABOLIC PROCESSES OF THE BODY. 



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 accumulate again afterward. Putting aside certain details, we may 

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

 ous salivary cell, a pancreatic cell, or a chief gastric cell ; and we may prob- 

 ably 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 bloodvessel, 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 take on the form of a network, the meshes 

 of which are wider arid more conspicuous 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 

 more 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 glycogeu, such as may be ex- 

 tracted from the liver, or, as seems more probable from its definite solu- 

 bility, glycogen in some more or less loose combination with some other 

 body, a combination, however, of such a kind that the iodine reaction makes 

 itself felt. 



377. The above may be taken as a general description of a cell in an 

 ordinary condition. The question now comes before us, What changes are 

 brought about by various foods or by the absence of food ? 



If a frog be largely fed on a diet containing large quantities of carbo- 

 hydrates, the liver will be found rich in glycogen, and the cells will present 

 the following characters: The cell is relatively large (cf. Fig. 114, A), and, 

 as it were, swollen ; the cell substance is largely occupied by the hyaline 

 material just spoken of, especially in its outer parts, so that in sections pre- 

 pared and mounted in the ordinary way in which the glycogen has been 

 dissolved out, the greater part of the cell 'consists of a loose open network of 

 bars of stained cell substance with wide meshes ; a certain quantity of more 

 solid, generally granular-looking cell substance occupies the part of the cell 

 nearest the lumen, and a thin shell of cell substance forms an envelope for 

 the rest of the cell. The nucleus is large and distinct, but though changes in 

 the nucleus accompanying changes in the cell substance have been described, 

 they are not sufficiently important to detain us now. When such a cell is seen 

 in a perfectly fresh state, the hyaline refractive material (which, we need 

 hardly say, gives a marked reaction with iodine) often hides the nucleus and 

 the greater part of the cell substance proper. 



If, on the other hand, the frog be fed on a proteid diet free from carbo- 

 hydrates for instance, on fibrin the liver contains little or no glycogen, 



