FATE OF THE CARBOHYDRATE FOOD-CONSTITUENTS. 667 



when on an amylaceous diet a larger proportion of the inspired oxygen 

 is returned to the atmosphere as C0 2 than when on animal diet. It 

 would appear, however, from the fattening which occurs on excessive 

 carbohydrate diet, that this oxidation is not complete, but that part of 

 the carbohydrates remain in the body. It has been already mentioned that 

 albuminoids may split up into fat, and it will be shown under the 

 statistical consideration of nutrition that the addition of carbohydrates 

 to a rich albuminous diet spares a certain amount of albumen from 

 destructive oxidation, and in this way carbohydrates may lead to the 

 deposit of fat. On the other hand, the connection between the carbo- 

 hydrates and fat must be closer than this, for bees on a pure diet of sugar 

 are able to manufacture wax, — a substance closely allied to the fats. 

 Besides, it has been shown that in the putrefaction of carbohydrates, in 

 addition to lactic, butyric, and caproic acids, fixed fatty acids are also 

 developed ; and, since a similar fermentation occurs in the alimentary 

 canal, it is possible that these fatty acids are in the body converted into 

 neutral fats. 



The seat of the oxidation of the carbohydrates is to be found 

 mainly in the muscles, as evidenced by the shortness of breath produced 

 by excessive muscular exertion, for it is only natural to suppose that the 

 more rapid breathing is to enable the body to get rid of the decom- 

 position products normally removed through the lungs, i.e., C0 8 , and to 

 introduce larger amounts of oxygen. The fact may, however, be proved 

 directly by estimating the C0 2 in the venous blood coming from a con- 

 tracting and resting muscle. That the C0 2 thus formed in muscular 

 action is from oxidation of the carbohydrate, and not albuminoid 

 muscle constituents, is proved by the following facts : An animal 

 in a given time accomplishes a certain amount of muscular work, and by 

 the estimation of the urinary constituents it may be determined how 

 much albumen has undergone oxidation. The comparison of the amount 

 of work represented by the combustion of this amount of albumen and 

 the amount actually accomplished shows that the latter must have been 

 at the expense of the combustion of some other substance than albumen. 

 This substance, in all probability, consists of carbohydrate material. 



In addition to the changes already sketched, the carbohydrates are 

 closely concerned in the function of glycogenesis, or the formation of 

 glycogen in the liver,— one of the processes of metabolic change which 

 has been most clearly localized. When comparative estimates are made 

 as to the amount of sugar contained in the hepatic and portal veins, 

 contrary to what would be expected, it will be found that in the hepatic 

 vein sugar is constantly found, even though none may be present in the 

 blood of the portal vein. So far, therefore, from destroying sugar, as was 

 formerly supposed, the liver is evidently concerned in the manufacture 



