CONSTANCY OF ENERGY KAT ABOLISH . 13 



Proportion of energy derived from protein — Buhner. 



Guinea pig. 



Dog. 



Rabbit. 



Day of 

 fasting. 



Protein ka- 

 tabolism in 

 per cent of 

 total ka- 

 tabolism. 



Day of 

 fasting. 



Protein ka- 

 tabolism in 



total ka- 

 tabolism. 



Day of 

 fasting. 



Protein ka- 

 tabolism in 

 per cent of 

 total ka- 

 tabolism. 



2 



Per cent. 

 10.4 

 11.1 

 11.0 

 11.9 

 11.8 

 6.9 

 11.2 

 10.9 



2-4 



Per cent. 

 16.3 

 13.1 

 15.5 

 17.4 

 20.0 



3 



Per cent. 

 16.5 

 23.6 

 26.5 

 29.8 

 50.1 

 96.4 



3 



10-11.... 

 12 



5-7 



4 



9-12. 





13 



13-15.... 

 16 



6 



14 



7 





17-18. . . . 



8 



9 





INFLUENCE OF SURPLUS PROTEIN. 



On the other hand, as Pettenkofer and Voit long ago showed, 1 

 when an animal which has been previously receiving large amounts 

 of protein is deprived of feed, the high protein katabolism which 

 is observed during the first two or three days of fasting is accom- 

 panied by a relatively smaller katabolism of fat. Thus in an experi- 

 ment with a dog, cited on a subsequent page (p. 7±) to illustrate 

 the initial fall of protein katabolism, respiration experiments were 

 made on the second, fifth, and eighth days, with the following 

 results : 



Katabolism of fasting dog — Toit. 



Day. 



Second dav 

 Fifth day 

 Eighth day 



Urinary 

 nitrogen. ! 



Fat ka- 

 tabo- 

 lized. 



Grams. Grams. 



11. 6 86 



5. 7 103 



4.7 99 



Protein ka- 

 tabolized in 

 per cent of 

 total ka- 

 tabolism. 



26.2 

 12.7 

 11.1 



Obviously we have here the reverse of what takes place in the later 

 days of fasting, viz, a gradual substitution of fat for protein as the 

 readily available supply of the latter in the body is reduced. Doubt- 

 less the effect would have been found to be still more marked on the 

 first day of the fasting, when the protein katabolism was equivalent 

 to 28.1 grams of nitrogen. 



RELATIVE CONSTANCY OF ENERGY KATABOLISM. 



The results which have just been considered regarding the nature 

 of the material katabolized in fasting and the way in which fat, 



1 Zeitschrift fiir Biologie, vol. 7, p. 369. 



