CHAP, iv.] METABOLIC PROCESSES OF THE BODY. 567 



iodine instead of brownish yellow as does ordinary cell-sub- 

 stance. 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 ap- 

 pear 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 conspicuous in the 

 outer part of the cell, in which the hyaline material was pre- 

 viously 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 

 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. 



361. 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. 106 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. When 

 such a cell is seen in a perfectly fresh state, the hyaline refrac- 

 tive material (giving the 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. 106 B). Little or no Iryaline 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 throughout. 



Lastly, if the frog be starved, and if to the effects of starva- 

 tion there be added those of exposure to a high temperature 



