GLYCOGENIC FUNCTION OF THE LIVER. 



745 



of starch, dextrin, and grape sugar, C 6 H 10 5 , but its general proper- 

 ties are intermediate between those of starch and dextrin. Like dex- 

 trin, when dissolved in water, gljcogen is immediately transformed 

 into grape sugar, by albuminoid ferments, as is proved by the solution 

 then decomposing the salts of copper, and turning the rays of polar- 

 ized light to the right hand, and also by its readily passing ihto the 

 alcoholic or the lactic acid fermentation. 



An amyloid or cellulose substance was long ago found in the Tuni- 

 cated animals (Schmidt), and amyloid bodies have since been observed 

 in other Non-vertebrate animals. (Carter.) In a peculiar degeneration 

 of various tissues and organs of the human body, as of the nervous sub- 

 stance, muscles, liver, spleen, kidneys, prostate, and other parts, amy- 

 loid bodies, or so-called corpora amylacea, have been frequently met 

 with. (Virchow, Meckel, Rouget.) Bernard himself detected a glyco- 

 genic substance in the placenta, and in various embryonic tissues, espe- 

 cially in the muscles, though he thought it disappeared from them in 

 after-life. Amyloid substance is sometimes certainly present in healthy 

 muscle ; it has been found in the muscles of the horse a few hours after 

 feeding, though, in the fasting condition, none is present. The occur- 

 rence of a starchy substance, is, therefore, as Rouget believes, by no 

 means confined to the tissues of vegetables, nor even to the liver 

 amongst the animal organs, but this substance may, under certain con- 

 ditions, be a product of the nutritive action of nearly all the tissues. 



The glycogenic function of the liver is, however, most remarkable, 

 and constitutes a special assimilative office, superadded to its ordinary 

 use of secreting bile. Since neither glycogen nor sugar is found in 

 the bile, it is obvious that, if this animal starch be employed in the 

 economy, it, or some product of it, must enter the blood, either di- 

 rectly through the veins, or indirectly through the lymphatics. It is 

 now known that, not the glycogen itself, but the sugar resulting from 

 its transformation, is absorbed by the hepatic veins. The detection 

 of considerable quantities of sugar in the blood of the hepatic veins 

 and of the right auricle of the heart, led, indeed, to the discovery of 

 the glycogenic function of the liver. At first it was supposed by Ber- 

 nard, that the sugar itself was formed by that organ. That this is 

 not derived directly from starch or sugar in the food, is shown by its 

 occurrence in animals killed after being fed, for at least a month, on 

 meat alone. That the sugar comes from the liver, is shown by the 

 fact, that after injecting water into the portal vein until the fluid es- 

 caping from the hepatic veins is colorless and free from sugar, it is 

 possible, after waiting a certain number of hours, to obtain by inject- 

 ing more water, a further supply of sugar. Hence Bernard concludes, 

 not merely that the sugar is produced in the liver, but that it must be 

 formed by a slow chemical, and not necessarily vital, change of an 

 amyloid substance within the liver. By treating the liver-substance 

 in the mode already mentioned, the glycogen is then obtained sepa- 

 rately. 



The transformation of starch into sugar, by salivin, suggested the 

 idea that this glycogen of the liver also requires a special ferment to 

 induce its metamorphosis. It was thought that, if not the salivin or 



