176 NUTRITION, DIETETICS AND ANIMAL HEAT 



ment of heat is also an invariable accompaniment of their 

 destruction. 



While a person may live on proteid food, the amount neces- 

 sary taxes the digestive and excretory organs to such an extent 

 that life is probably shortened. Since the total amount of urea 

 is discharged by the kidney, that organ, under an excess of pro- 

 teid diet, is particularly prone to degenerative changes of a most 

 serious nature. 



2. The carbohydrates enter the blood from the alimentary 

 canal as dextrose, are conveyed to the liver and converted into 

 glycogen, which is stored up there to be dealt out to the blood 

 gradually, after being reconverted into dextrose. Dextrose 

 exists in the blood for a short time only, being converted into 

 other substances, but its final oxidation is effected by the tissues. 

 Its end products are carbon dioxide and water, with heat. 

 Sugar (dextrose) injected into the blood soon disappears. It is 

 thought by some to be converted into alcohol in the blood and 

 then oxidized. At any rate, the formation of the end products 

 just mentioned is the final fate of the carbohydrates, through 

 whatever splitting processes the sugar molecule may pass before 

 it is converted into these substances. 



The removal of the pancreas occasions diabetes mellitus, and 

 the inference is that this gland gives off to the blood some internal 

 secretion which splits up the sugar molecule in the blood. How 

 this lesion causes the disease in question is not clear, but the 

 retention of a small part of the gland enables the oxidation of 

 sugar by the tissues to proceed in the proper way and it is not 

 discharged in the urine. 



Value of the Carbohydrates in Nutrition. The distinctive 

 function of the carbohydrates is to act as fuel for the body ma- 

 chine; they are burnt up to supply heat, and heat represents 

 energy. Hydrogen and oxygen exist already in the proportion 

 to form water one of the end products and only enough O 

 is required to unite with the carbon of the carbohydrates to form 



