THE FASTING METABOLISM. . 81 
and subsequently the total metabolism as shown by the combined 
nitrogen and carbon balance. 
§ 1. The Proteid Metabolism. 
TENDS TO Become Constant.—When food is withheld from a 
well-nourished animal, particularly a carnivorous animal, the proteid 
metabolism usually diminishes, at first rapidly and more slowly later, 
until within a few days it reaches a minimum value which may then 
remain nearly unchanged for a considerable time. This was first 
shown by the investigations of Carl Voit, in conjunction with 
Bischoff and later with v. Pettenkofer, and has been fully confirmed 
by later results. 
The following table shows the results obtained by Voit * in 
several experiments upon a dog weighing about 35 kgs., the pro- 
teid metabolism being expressed in grams of urea per day. As 
noted in Chapter III, such results are not absolutely accurate and do 
not represent the total proteid metabolism, but the fact that they 
are comparable is sufficient for our present purpose. 
Previous Food per Day. 
00 Meats | 1500 6 1500 G 
‘| G 5 rms. rms. F 
Meat | 250 Gras, | Meat. "| Meat. "| Nothing. 
Fat. 
Urea per day: Grms. Grms. Grms. Grms. Grms. 
Last day of feeding....| 180.8 180.0 110.8 110.8 24.7 
1st ‘ ‘* fasting..... 60.1 37.5 29.7 26.5 19.6 
Sd se Me giacttinss 24.9 23.3 18.2 18.6 15.6 
8d ME gaxsie 19.1 16.7 17.5 15.7 14.9 
4th “ « Me | hia 17.3 14.8 14.9 14.9 13.2 
Sth “ <« OO eases 12.3 12.6 14.2 14.8 12.7 
6th “ « fe Steers 13.3 12.8 13.0 12.8 13.0 
%th “« « SS siitetase 12.5 12.0 12.1 12.9 
8th “ * SE: stewie 10:1. |e scs.ccnen 12.9 12.1 
Sth “« ME achiairs | oa tovand eaeve ['evksa'ayaheheeee| Orase aes BhS 11.9 
10th “ “ GS “roo toca lig gcahtstgravalts os [arevar troy eecail [ies eens a 11.4 
Two Facrors or Prorerp Metapouism.—In these, as in many 
similar experiments, the proteid metabolism was quite unequal on 
the last day of the feeding and on the first fasting day, but in a 
* Zeit. f. Biol., 2, 311. 
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