5IO THE LIVER. [CH. xxxm. 



a fact that increase of carbohydrate food leads to the formation 

 of fat in the body and in the liver-cells. In support of the theory 

 that glycogen may also lead to the formation of proteids, he has 

 shown that many proteids contain a carbohydrate radicle. 



The whole question is in a very unsettled state, and is under 

 keen discussion at present. We may state, however, that the 

 prevalent opinion is that the liver-cells may be able to convert 

 part of the store of glycogen into fat, but that most of the 

 glycogen leaves the liver as sugar, so justifying the name (literally, 

 mother substance of sugar) given to it by Bernard. 



Carbohydrate metabolism is thus a series of hydrations and 

 dehydrations before combustion finally occurs. Starch is first 

 hydrated in the alimentary canal to form sugar. This passes to 

 the liver, where it is dehydrated to form glycogen, or animal 

 starch ; and finally hydrated once more to pass to the tissues as 

 sugar, where it undergoes combustion. 



Diabetes. In certain disorders of hepatic metabolism, the 

 glycogenic function is upset, and excess of sugar passes into the 

 blood, leaving the body in the urine (glycosuria) . This may be 

 due to an increased formation of sugar from glycogen, or to a 

 diminished formation of glycogen from the sugar of the portal 

 blood, according as either Bernard's or Pavy's view of the liver 

 function is adopted. In many cases the diabetic condition may 

 be removed by a close attention to diet ; starchy and saccharine 

 food must be rigidly abstained from. 



In other eases, which are much more serious, diet makes little 

 or no difference. Under these circumstances the sugar must come 

 from the metabolism of the proteid constituents of protoplasm. 



The disease diabetes is not a single one ; the term includes 

 many pathological conditions, which all possess in common the 

 symptom of excess of sugar in the blood and urine. 



'A diabetic condition may be produced in animals artificially in 

 several ways : 



(1) By diabetic puncture. Claude Bernard was the first to 

 show that injury to the floor of the fourth ventricle in the region 

 of the vaso-motor centre leads to glycosuria. The injury produces 

 a disturbance of the vaso-motor mechanism, but diabetes cannot 

 be regarded as purely vaso-motor in origin. 



This condition is of interest, because brain disease in man, 

 especially in the region of the bulb, is frequently associated with 

 glycosuria. 



(2) By extirpation of the pancreas. This is alluded to on 



P- 493- 



(3) By administration of phloridzin. Many poisons produce 



