530 TEXT-BOOK OF PHYSIOLOGY 



hence there is a general belief that destructive disease of the pancreas or a 

 defective production of its activating hormone is the most frequent cause 

 of diabetes. 



From the foregoing facts it is clear that a glycosuria more or less pro- 

 nounced may be due to the following causes: 



1. An imperfect abstraction of sugar from the portal blood and its storage 



as glycogen by the liver cells. 



The imperfect abstraction and storage of sugar may be due to an impair- 

 ment in the functional activities of the liver cells or to the ingestion and 

 absorption of excessive quantities of sugar from the intestine. In the 

 latter instances the resulting glycosuria is said to be of alimentary origin. 



2. A too rapid conversion of glycogen to sugar on the part of the liver cells 



(glycogenesis or glycogenolysis). 



The increased conversion of glycogen to glucose may be due to in- 

 creased activity of the area in the medulla, controlling sugar production, 

 the so-called "diabetic area/' in consequence of the arrival of nerve im- 

 pulses developed by traumatic conditions in various regions of the body, or 

 developed by the occurrence of major emotional states. In all instances 

 the adrenal glands are believed to be simultaneously stimulated to in- 

 creased activity and to an increased discharge of adrenalin into the blood, 

 which in turn leads to a heightening of the irritability of the nerve endings 

 of the hepatic plexus whereby arriving nerve impulses become more 

 effective. 



3. An incomplete oxidation of sugar (glycolysis) in the cells of muscle and 



perhaps other tissues as 'well, in consequence of which it accumulates 

 in the blood beyond the normal amount, thus establishing the condition 

 of hyperglycemia. 



The imperfect oxidation of sugar in the muscle-tissue is probably the 

 result of an absence of the necessary glycolytic enzymes or to the 

 absence of the apparently necessary activating hormone from the 

 pancreas. The more rapid metabolism of the protein constituents 

 of the tissues whereby their glucose radicals are liberated in large 

 amount may be necessitated by the inability to oxidize the sugar 

 normally brought to them by the blood. 



The final disposition of sugar in the body is an oxidation to carbon 

 dioxid and water. The chief if not the only intermediate stage is lactic 

 acid. It appears from chemical relations that the molecule of sugar is trans- 

 formed into two molecules of lactic acid and these in turn into carbon dioxid 

 and water. In its final oxidation the contained energy is liberated as heat. 



