32 PHYSIOLOGY CHAP. 



are added to the diet of meat the protein consumption diminishes ; 

 with the addition of this food-stuff the animal can preserve its 

 store of flesh, and increase this reserve on a smaller amount of 

 meat. The saving in the consumption of flesh brought about by 

 saccharides is greater than that caused by an equal quantity of fat. 

 This explains why herbivorous animals put on flesh quickly 

 when their food contains a large quantity of carbohydrate. 



There is a minimum limit to the amount of meat which in 

 conjunction with saccharides must be taken in order to maintain 

 nitrogenous equilibrium ; if this limit is not reached the animal 

 will lose flesh. The limit is lower in fat non-fleshy organisms, 

 higher in lean fleshy organisms. 



Carbohydrates not only effect a saving in the consumption of 

 flesh, but also in the consumption of fat, and therefore increase 

 the amount of fat in the body (Voit). 



Liebig, taking into consideration the well - known fact that 

 animals (pigs, geese) which are to be fattened are given large 

 quantities of carbohydrate and only small quantities of protein, 

 was the first to propound the theory that saccharides are trans- 

 formed into fats. Against this theory Voit set up that of sparing, 

 according to which the increase of fat is due to the fact that 

 the saccharides lessen the combustion of fats, which therefore 

 accumulate in the organism. We have, however, in the treat- 

 ment of the complex subject of the formation of fat, shown the 

 correctness of Liebig's theory according to the successive investi- 

 gations of Munk, Tscherwinsky, Meissel and Strohmer, and of 

 Rubner (vide Vol. II. Chap. V. 12). 



It is necessary to lay stress upon the fact that saccharides 

 are more readily decomposed than fat, either taken in as food or 

 stored up in the body. When a little starch or sugar is added 

 to an abundant diet of meat, an increase in the quantity of carbon 

 dioxide discharged by the animal is immediately observed ; when, 

 on the other hand, fat is added, there is no change in the quantity 

 of carbon dioxide discharged (Voit). If a fasting dog be given a 

 certain amount of carbohydrate after the value of its respiratory 

 quotient has been ascertained and time allowed for intestinal 

 absorption, we shall find an increase in the respiratory quotient, 

 which proves the rapid oxidation of the food given (Magnus- 

 Levy). 



The calorimetrical researches made by Atwater, of which we 

 shall treat in the next chapter, not only confirm the theory that 

 saccharides are easily oxidised, but prove that with a mixed 

 diet which contains a large quantity of saccharides, these 

 substances are the first to burn, the combustion of the fats 

 contained in it only beginning when the saccharides have been 

 entirely consumed. 



IX. We must now ascertain the value as regards metabolism of 



