METABOLISM, ANABOLISM AND KATABOLISM 393 



of the excretions. The twenty-one inorganic matters belong to a class 

 of substances that pass through the body unchanged. 



The carbohydrates undergo important changes in the body. They 

 are oxidized and converted into carbon dioxide and water, contributing 

 to the production of animal heat and force. Oxidation of the carbo- 

 hydrates is one of the sources of water produced in the economy. 



The probable mechanism of the transformation of the carbohydrates 

 by oxidation into carbon dioxide and water was foreshadowed by Ford, 

 an American physician, in 1872. This observer obtained a small quan- 

 tity of alcohol from the blood of the ox, which he assumed was derived 

 from the carbohydrates. The results of these experiments, however, 

 were not confirmed by certain German physiologists and were dis- 

 credited ; but recently (1904), Stolaska has extracted from the blood 

 of the ox, the heart of the dog and the pancreas of the pig, a glycolytic 

 enzyme capable of producing alcohol. This writer regards " alcoholic 

 fermentation as the first stage of the respiratory process." 



The modern trend of physiological opinion is toward the idea that 

 alcohol, in doses so small that it may be promptly oxidized, is not harm- 

 ful, although, when alimentation is sufficient, it is unnecessary. Its oxi- 

 dation produces energy, like the oxidation of so-called carbonaceous 

 foods, notably the carbohydrates. In this connection a study of diabetes 

 mellitus is most instructive. It is thought by some pathologists that 

 this disorder is due, in many instances, to absence of an enzyme, nor- 

 mally produced in the pancreas, that acts on carbohydrates. It is 

 thought, also, that all the energy due to oxidation of carbohydrates 

 comes from the final oxidation of alcohol which results from the action 

 of enzymes in the blood on sugar, and that carbohydrates can not be 

 utilized as producers of heat and force in any other way. All the car- 

 bohydrates oxidized in the body pass into the general circulation by the 

 hepatic veins. As early as 1888, I wrote " It is reasonable to suppose 

 that the small quantity of sugar constantly discharged into the blood by 

 the liver is converted into alcohol, which is promptly oxidized, being 

 converted into carbon dioxide and water." 



The fats undergo oxidation in the body ; and this oxidation con- 

 tributes to the production of animal heat and force. As a rule the 

 fats exist in the organism in combination with each other but are not 

 combined with proteids. 



Oxygen exists in the red blood-corpuscles combined with hemoglobin. 

 Carbon dioxide exists in solution in the blood, lymph, chyle and secreted 

 liquids. Nitrogen, carburetted hydrogen and hydrogen monosulphide 

 exist in a gaseous state in the alimentary canal. A small quantity of 

 nitrogen exists in solution in the blood. 



