LECTURE XIV. 



THE MUTUAL RELATIONS BETWEEN FATS, CARBO- 

 HYDRATES, AND ALBUMINS. 



I. 



IN our previous treatment of the three most important classes of organic 

 food-stuffs, the fats, carbohydrates, and albumins, we have considered each 

 individual group by itself, as regards the way in which it is absorbed, the 

 place where it is assimilated, and the relations of the group to specific 

 functions of the body. We have found that carbohydrates are the most 

 important source of muscular power, while in the fats we have the princi- 

 pal source of heat. The significance of the albumins is much less certain. 

 We know that they are absolutely unreplaceable, and also that they act 

 as building material for the cells, being necessary to replace the parts 

 which have been used up. We do not at present understand why the 

 animal organism requires so much albumin under all conditions, nor 

 why it so quickly decomposes, up to a certain limit, the ingested 

 albumin. 



By more closely following the metabolism, we quickly encounter results 

 which do not harmonize, for example, with the assumption that the mus- 

 cles are only capable of acting by means of the energy given to them by 

 the carbohydrates. Again, it was noticed early that a portion of the car- 

 bohydrates disappeared when the diet was rich in these substances, i.e., 

 this part could not be detected in the form of glycogen, and, moreover, 

 an exact study of the respiratory exchange showed that no increased com- 

 bustion of the sugars had taken place. According to this we can only 

 assume that the extra carbohydrate is retained in some form other than 

 glycogen. 



Before discussing those facts, which force us to the assumption that a 

 transformation of one group of food-stuffs into another may take place 

 in the animal organism, we will first of all call attention to the relations 

 existing between fats, carbohydrates, and albumins, according to our 

 present knowledge regarding the chemical composition of these substances. 

 Of course, this will only show us the possibility of such transformations, 

 and indicate the manner in which they may take place. The organism 

 itself may, naturally, choose an entirely different course, and utilize other 



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