FATS, CARBOHYDRATES, AND ALBUMINS. 



347 



indicate that the carbohydrates are attacked immediately after absorption 

 from the intestine, thus sparing the body fat. We must not forget, with 

 regard to such experiments, that the conclusions drawn are for the most 

 part indirect. They are not conclusive. A comparison of the general 

 metabolism on the basis of income and outgo alone, must necessarily lead 

 to a one-sided decision. The results of physiological-chemical investi- 

 gations must not be left out of consideration, and the finer details of the 

 work must not be forgotten in studying the coarser outlines of metabolism 

 as a whole. We have seen that the metabolism of carbohydrates in all 

 of its phases is an extremely delicately regulated process. Sugar reappears, 

 after absorption, in the liver, deposited in the form of glycogen. This 

 does not vanish so easily. It is extremely difficult to obtain an animal 

 which is free from glycogen. At all events, our knowledge regarding the 

 transformation of the carbohydrates in the tissues is altogether opposed to 

 the assumption that they are rapidly burned up after absorption, even 

 during work. We know it is true that the muscles evidently prefer to 

 utilize the energy from carbohydrates in their performance of work, but 

 this very fact prevents us from believing that the organism consumes this 

 valuable material in order to save the fats. 



Studies on metabolism have shown us that there is a difference in the 

 behavior of the protein in food and that of fats and carbohydrates, 

 which are themselves very similar in their behavior. We have already 

 stated that by increasing the amount of protein in food, there is an in- 

 creased metabolism. This, however, is not the case, or at least not to the 

 same extent, if we increase the quantities of fat or carbohydrate, as the 

 following experiments, carried out by M. Rubner, show: 



2, 4, 6, and 8 are fasting experiments. In them 40.4 calories per kilo- 

 gram body weight is the average metabolism. The addition of albumin 

 causes an increase in the number of calories amounting to 11.9 per cent; 

 the addition of fat, 1.2 per cent; and that of carbohydrates, 4.2 per cent. 



