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THE METABOLISM OF FAT 



Both the respiratory exchange and the urinary nitrogen per kg. 

 of live weight remain approximately constant (Lehmann, Zuntz). 

 The proteid metabolism tends to a somewhat uniform percentage 

 of the total, namely, from 10 per cent, to 14 per cent., and only 

 begins to increase in the final stage of starvation when the reserve 

 of depot fat is almost exhausted, and there is increasing difficulty 

 in transferring an adequate amount of fat from the adipose tissue 

 to the blood. If the body be well nourished and contain much 

 fat this increase in proteid katabolism may be long deferred. 



The following example illustrates this : 



In a rabbit, on the other hand, the proteid metabolism was 25 

 per cent, of the whole by the eighth day, 50 per cent, by the six- 

 teenth day, and 964 per cent, by the seventeenth to eighteenth day. 



The rise in proteid coincides with the exhaustion of the supply 

 of visible fat. 



As the fasting herbivorous animal comes to live on its own fat 

 it is interesting to note how the respiratory quotient changes from 

 a carbohydrate to a fat value. 



Guinea-pig (Finkler). 



THE METABOLISM OF FAT WHEN PROTEIDS ARE FED 



When proteids are fed, the proteid metabolism which equals 

 only 10-14 per cent, of the whole day's energy in the fasting 

 animal becomes greatly stimulated, and a large proportion of 



