176 NUTRITION, DIETETICS AND ANIMAL HEAT 



an extent that life is probably shortened. Since the total 

 amount of urea is discharged by the kidney, that organ, un- 

 der an excess of proteid diet, is particularly prone to degen- 

 erative 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. Dex- 

 trose exists in the blood for a short time only, being con- 

 verted into other substances, but its final oxidation is ef- 

 fected 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 con- 

 verted 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 split- 

 ting processes the sugar molecule may pass before it is con- 

 verted 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. Hbw 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 

 machine ; they are burnt up to supply heat, and heat repre- 

 sents 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 CO2 the other end product. The 

 burning (oxidation) of a carbohydrate outside the body re- 

 sults in the formation of CCte and H2O and the elimination 

 of heat, which last, if properly utilized, can be converted into 

 energy the power to do work. The result of the oxidation 



