522 TEXT-BOOK OF PHYSIOLOGY 



It is, therefore, apparent that the phenomena of diabetes in man closely 

 resemble the phenomena that arise in animals when the pancreas is removed; 

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

 most frequent cause of diabetes. 



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

 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 impair- 

 ment of the nerve-centers regulating the normal process or to stimula- 

 tion of the liver cells by one or more hormones discharged into the blood 

 in unusual quantities by some organ of internal secretion, e.g., adrenalin. 

 See page 504. 



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. The more 

 rapid metabolism of the protein constituents of the tissues whereby 

 their glucose radicals are liberated in large amount maybe 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. 



