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PHYSIOLOGY 



output per square metre of surface has been reckoned for a number of 

 animals of different weight : 



Speaking roughly, we may say that a warm-blooded animal during 

 starvation requires the daily expenditure of 1000 calories per square metre 

 body surface in order to maintain its temperature and carry out such motor 

 processes as are essential to life. 



THE METABOLISM OF CARBOHYDRATE, FAT, AND 

 PROTEIN DURING STARVATION 



Since during starvation no energy is supplied to the body from without 

 in the shape of food-stuffs, we can regard the whole expenditure of the 

 animal during its period of starvation as occurring at the expense of its 

 capital. The amount of carbohydrate which can be stored up as glycogen or 

 other forms is strictly limited. In many experiments the glycogen meta- 

 bolism has therefore been entirely disregarded, and it has been estimated that 

 the chemical capital of the body consisted entirely of proteins and fats. 

 The glycogen metabolism, however, during the first day of a period of starva- 

 tion may form a considerable fraction of the total metabolism of the body, 

 and can hardly be excluded without introducing serious errors. The 

 relative parts played by protein, carbohydrate, and fat respectively in the 

 chemical exchanges of a starving animal may be determined in the following 

 way : The amount of protein consumed is given by estimating the total nitro- 

 gen of the excreta by Kjeldahl's method and multiplying the result by the 

 factor 6-25. The loss of weight of the body minus the protein consumed may 

 be roughly taken as equivalent to the fat plus carbohydrate consumption. 

 But this is only a rough method, since the quantity of water in the tissues 

 may undergo considerable variations, and so affect the total weight of the 

 body. For any accurate results the respiratory exchanges must be measured 

 including both oxygen intake and carbon dioxide output. After deducting 

 the carbon dioxide due to the combustion of the carbon of the proteins which 

 does not appear in the urine in combination with nitrogen, the remainder of 

 the carbon dioxide is derived entirely from carbohydrate and fat metabolism. 

 Knowing the respiratory quotient and the total amount of carbohydrate and 

 fat metabolism, it is possible to come to a conclusion as to how much of the 



