METABOLISM, NUTRITION AND DIETETICS 447 



sugar by amylolytic ferments, is present in large amount. 

 (See Practical Exercises, p. 511.) 



(2) The liver after the death of the animal is left for a time 

 in situ, or, if excised, is kept at a temperature of 30 to 40 C., 

 or for a longer period at a lower temperature ; it is then 

 treated exactly as before, but no glycogen, or comparatively 

 little, can now be obtained from it, although sugar (dextrose) 

 is abundant. The inference plainly is that after death the 

 hepatic glycogen is converted into dextrose by some influence 

 which is restrained or destroyed by boiling. This influence 

 may be due to an unformed ferment or to the direct action of 

 the liver-cells, for both unformed ferments and living tissue 

 elements are destroyed at the temperature of boiling water. 

 Although there is no doubt that an amylolytic ferment can 

 be extracted from the liver in small amount, as from other 

 organs and from the blood, it has been shown that the vital 

 action of the hepatic cells is the most important factor. The 

 amylolytic activity of a fresh liver, for instance, is increased 

 by chloroform, but this is not the case with a liver which has 

 first been treated by alcohol and dried, and in which accord- 

 ingly the cells have been killed while the unorganized 

 ferments are unaffected (Paton). And sulphate of quinine, 

 which does not hinder the activity of enzymes, causes when 

 injected into the veins a diminution in the amount of sugar 

 formed in the liver (Cavazzani). The post-mortem change is 

 to be regarded as an index of a similar action which goes on 

 during life : sugar in the intact body is changed into glycogen ; 

 glycogen is constantly being changed into sugar. 



(3) With the microscope, glycogen, or at least a substance 

 which is very nearly akin to it, which very readily yields it, 

 and which gives the characteristic port-wine colour with 

 iodine, can be actually seen in the liver-cells. The liver 

 of a rabbit or dog which has been fed on a diet containing 

 much carbo-hydrate is large, soft, and very easily torn. Its 

 large size is due to the loading of the cells with a hyaline 

 material, which gives the iodine reaction of glycogen, and is 

 dissolved out by water, leaving empty spaces in a network 

 of cell-substance. If the animal, after a period of starvation, 

 has been fed on proteid alone, only a little glycogen is found 



