NITROGEN METABOLISM DURING CHRONIC UN- 



DERFEEDING AND SUBSEQUENT 



REALIMENTATION 



In the course of an extended physiological investigation of the 

 effects of chronic underfeeding, a number of observations on the 

 nitrogen metabolism have been made which will be briefly discussed 

 in this preliminury note. 



The experiments were made with a dog weighing 14 kg. The 

 animal was fed a very liberal, but not excessive, diet for ten days. 

 During this time it was found that 78.7 percent of the absorbed 

 nitrogen had been eliminated by the kidneys. The quantity of food 

 was then reduced to one-third, so that in the course of several weeks 

 the dog was obliged to live at the expense of its own tissues. The 

 amount of nitrogen in the food was very low, which circumstance 

 caused a continuous waste of the nitrogenous material of the body. 

 Correspondingly, the nitrogen eliminated in the urine for the first 

 week of underfeeding was 85.4 percent above the amount actually 

 absorbed. 



The supply of nitrogen during the period of chronic starvation 

 varied from 21.7 to 23.1 gm., per w-eek. The nitrogen elimination 

 remained very uniform until a late period in the experiment, when 

 quite abruptly it increased about 25 percent. This increased nitro- 

 gen elimination coincided with a series of interesting changes in the 

 animal which cannot, however, be alluded to here. It was occa- 

 sioned by a greater combustion of protein, due to the exhaustion of 

 the fat of the body. The specific gravity of the daily urines throws 

 some light on this matter. The average sp. gr. of the normal urine 

 was 1.0141, while during the early part of the underfeeding it was 

 1.0124. In the concluding two weeks the sp. gr. rose to 1.0186 

 (the volume being practically the same), owing to the liberation of 

 inorganic substances by the protein decomposition. The study of 

 the gaseous exchange and the respiratory quotients furnished fur- 

 ther unequivocal proof that the organism derived its energy from 

 the oxidation of the muscular substance. 



After the animal's weight had diminished over 40 percent, and 

 its physical strength had been reduced to such an extent that it was 

 unable to enter its cage but had to be lifted into it, the dog was 

 again given a rieh diet ; and in f our weeks time it f ully recovered the 



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