THE MINIMUM OF PROTEIN. 



75 



Benedict, cited on page 15 in illustration of the relative constancy of 

 the energy katabolism, the total protein katabolism showed a distinct 

 falling off, and the same is true in less degree when computed per 

 kilogram weight. The total urinary nitrogen upon the several days 

 of the experiment was : 



Protein katabolism of fasting man — Benedict. 



Days. 



Urinary nitrogen. 



Days. 



Urinary nitrogen. 



Total. 



Per kilo- 

 gram 

 weight. 



Total. 



Per kilo- 

 gram 

 weight. 



1 



Grams. 

 12. 24 

 12.45 

 13.02 

 11.63 



Gram. 

 0.206 

 .211 

 .223 

 .202 



5 



Grams. 

 10. 87 

 10. 74 

 10.13 



Gram. 

 0. 191 

 .190 

 .181 



2 



6 



3 



7 



4 





E. and O. Freund 1 determined the daily nitrogen excretion of Succi, a pro- 

 fessional faster, with the following results: 



Protein katabolism of fasting man — E. and O. Freund. 



Days. 



Nitrogen. 



Days. 



Nitrogen. 



Days. 



Nitrogen. 



1 



Grams. 

 17.0 

 11.2 

 10.55 

 10.8 

 11.19 

 11.01 i 

 8.79 j 



8 



Grams. 

 9.74 

 10.05 

 7. 12 

 6.23 

 6.84 

 5.14 

 4. 66 



15 



Grams. 

 5.05 

 4. 32 

 5.4 

 3.6 

 5.7 

 3.3 

 2. 82 



2 



9 



16 



3 



10 



17 



4 



11 



18 



5 



12 



19 



6.. 



13 



20 



7 



14 



21 









A similar phenomenon was observed by Michaud in experiments on the rela- 

 tive value of proteins described on a subsequent page. A dog, after 44 days ab- 

 stinence from protein (16 days without food followed by 2S on nonnitrogenous 

 food), excreted daily 1.42 grams nitrogen. The same dog after prolonged feeding 

 upon low protein rations, however, showed in a three-days fast an average daily 

 excretion of only 0.95 grams nitrogen. On the other hand, however, as already 

 pointed out, the fasting protein katabolism may show a very marked increase 

 with the progress of fasting in the absence of a sufficient store of body fat. 

 It appears, then, that in fasting the protein katabolism is much more variable 

 in amount than the total katabolism, and this fact must be remembered in any 

 discussion of the protein requirement. 



THE MINIMUM OF PROTEIN. 2 



It is evident that the comparatively small amount of protein kata- 

 bolized in the fasting animal so long as its store of fat is reasonably 

 abundant is at least all that is absolutely essential to the vital 



1 Cited by Lusk. 



2 For a more exhaustive discussion of the subjects of this and succeeding paragraphs, 

 including references to the literature, compare the references on page 8, in particular 

 Magnus-Levy, pp. 198-423 ; Tigerstedt, pp. 391-480 ; Lusk, Chapters IV and V. 



