720 GLYCOGEN IN HEPATIC CELLS. [BOOK n. 



glycogen such as may be extracted from the liver, or, as seems 

 more probable from its deficient solubility, 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. 



457. 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 

 carbohydrates, the liver will be found rich in glycogen and the 

 cells will present the following characters. The cell is relatively 

 large (cf. Fig. 92 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 prepared 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 

 carbohydrates, for instance on fibrin, the liver contains little or no 

 glycogen, and the hepatic cells are not only much smaller but 

 present an appearance very different from the above (cf. Fig. 92 B). 

 Little or no hyaline material is visible, the cells give little or no 

 port-wine reaction with iodine, but only the usual brown yellow 

 proteid reaction, and in specimens prepared and mounted in the 

 ordinary way the cell-substance appears densely granular through- 

 out. 



Lastly, if the frog be starved, and if to the effects of starvation 

 there be added those of exposure to a high temperature (25), by 

 which as we have seen the hepatic cells are markedly affected, the 

 liver is found to be free from glycogen*, and the hepatic cells to be 

 extremely small (cf. Fig. 92 c), only half the size or even less, of 

 those of the well-fed frog, but otherwise much like the cells in a 

 frog fed on proteid material. 



458. In the mammal changes in the hepatic cells similar to 

 those just described as occurring in the frog have also been 

 observed. When the animal is fed on a diet rich in carbohydrates, 

 and when therefore as we have seen the liver abounds in glycogen, 

 the hepatic cells (Fig. 93) are larger (so large that they have 



