FATE OF THE CARBOHYDKATE FOOD-CONSTITUENTS. 669 



three times the degree possessed by grape-sugar ; it is inodorless and 

 insoluble in alcohol or ether. Under the action of the salivary or pan- 

 creatic ferments, namely, diastase, or the action of dilute mineral acids, 

 it is converted, like other carbohydrates, into a mixture of maltose and 

 dextrin. Its formula may be given as a multiple of C 6 H 10 O 6 . 



Glycogen is not confined to the liver-cells, although its presence may 

 be recognized there by treating a section of hepatic tissue with iodine, 

 when it may be recognized by the characteristic red staining with iodine 

 in the neighborhood of the cell-nucleus. It is present, also, in the pla- 

 centa, in muscular tissue, white blood-cells, the brain, and in various 

 embryonic tissues. From the fact that it is found in largest amount 

 in growing tissue it would appear to be especially concerned in the 

 phenomena of development. 



The amount of glycogen which may be present in the liver varies in 

 very wide amount, from a maximum to an absolute absence, the amount 

 being dependent upon the state of the nutrition of the animal. If a 

 rabbit is allowed to starve to death, and its liver be treated as described 

 above, it will be found that the decoction of the liver will be absolutely 

 free from glycogen. In other words, it would appear that the glycogen 

 is derived from the food-stuffs which are absorbed by the walls of the 

 alimentary tract and are carried by the portal vein to the liver. If it 

 be determined by experiment how long starvation must be continued to 

 remove all traces of glycogen from the liver, and after the lapse of such 

 an interval the animal be abundantly supplied with carbohydrate food 

 and then killed, it will be found now that the liver has regained its 

 store of glycogen, and that the decoction now made will show the maxi- 

 mum quantity of glycogen present. If after starving for the same length 

 of time the animal be fed with a meat diet, a certain amount of glycogen 

 will also be detected in the liver, but in much less amount than after the 

 carbohydrate diet. 



The question arises at this point as to whether the glycogen so 

 developed originates from the albuminous constituents of the meat diet, 

 as it is known that meat, especially the meat of the horse, which is em- 

 ployed in such experiments, contains representatives of the carbohydrate 

 group. This question may be settled by substituting a pure albuminous 

 substance as diet, and it will then be found that although the amount of 

 glycogen obtainable from the liver is larger than that obtained from a 

 starving animal, it still falls below the amount obtained after feeding 

 with meat. It would, therefore, appear that the development of glycogen 

 on the meat diet is only partially due to the conversion of the albuminous 

 constituents of the food into glycogen, but mainly to the carbohydrate 

 constituents. 



If a starving animal be fed on a fat diet, even though abundant, no 



