THE HISTORY OF GLYCOGEN. 



443 



and the hepatic cells are not only much smaller, but present an appearance 

 very different from the above (cf. Fig. 114, B). Little or no hyaline mate- 

 rial 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 starvation there be 

 added those of exposure to a high temperature (25 C.), 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. 114, 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. 



378. 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. 115) are 

 larger (so large that they have by some authors been described as com- 

 pressing the lobular capillaries) and loaded with the same refractive hya- 

 line material staining port-wine red with iodine. When this material is 

 dissolved out a coarse open network of cell substance is displayed. The 



FIG. 115. 



FIG. 116. 



Section of Mammalian Liver rich in Gly- Section of Mammalian Liver containing 



cogen. (Langley.) Osmic acid specimen, gly- little or no Glycogen. (Langley.) Osmic 



cogen not dissolved out. acid specimen. The granules are not well 



preserved in some of the cells. 



most marked point of difference between the mammalian and frog's hepatic 

 cell under these conditions is that in the former, the hyaline glycogenic sub- 

 stance is gathered at first centrally around the nucleus (not more on the outer 

 side, as is the case in the frog) and spreads from the centre toward the pe- 

 riphery, always leaving on the extreme outside a somewhat thick shell of 

 cell substance, which in hardened and prepared specimens may strikingly 

 simulate a thickened cell- wall. We may add that in an animal thus fed the 

 whole liver is very large, and, as it were, swollen ; it is also soft and tears easily. 



In an animal fed on proteids alone, for instance on fibrin, the liver fre- 

 quently contains some glycogen and the hepatic cells contain a small quantity 

 of hyaline glycogenic material. As in the corresponding case in the frog, 

 the cells are comparatively small, and the cell substance appears finely and 

 uniformly granular. 



In a starved mammal the liver is small, dense to the touch, and tough ; 

 it contains a trace only of glycogen or none at all ; the cells (Fig. 116) are 

 small, as it were shrunken, and the cell substance, which gives no port-wine 

 reaction, or a mere trace only, with iodine, is still more finely granular. 



379. The microscopic appearances just described show, and indeed 



