THE RELATIONS OF METABOLISM TO FOOD-SUPPLY. 117 
Nitrogen Digested. : Nitrogen io Urine. 
Basal Ration, Basal Ration Basal Rati Basal Ration 
Grms. eee "ae on ay h, 
OX Dsiie woe Soran Bilidet a 135.30 118.40 122.54 104.69 
OX. vc ced s vawee eee 111.67 107 .55 106 .03 81.18 
Ox secuee kia ks We 86.27 80.92 86.30 63.83 
OX ie erciaster acne 4 116.51 94.66 109.28 81.71 
OR Dios aiccos ewan ceased 128.11 118.18 122.62 103.13 
Since the addition of starch to the basal ration diminished the 
apparent digestibility of the protein, the effect is most clearly seen 
by comparing the daily gains of nitrogen by the animals on the 
two rations, as follows: 
n Bas . With Addition ' . 
On B Bae Bey of ‘Starch, Difference. 
OX) ee ashatna sinner centeeahes 12.76 13.71 + 0.95 
ORM enka, chee whan 5.64 26.37 +20.73 
ORG wee see dShalle ated acento —0.03 17.09 +17.12 
OR Els oc ceniammavn neat illness 7.23 12.95 + 5.72 
OX Jigs oo ene eos Me ase 5.49 15.05 + 9.56 
Cellulose—The peculiar position occupied by cellulose, as the 
essential constituent of the “crude fiber” of feeding-stuffs, in the 
nutrition of domestic animals causes much interest to attach to the 
study of its effects upon metabolism. We shall consider here only 
its effects upon the proteid metabolism. 
The first to take up this subject appears to have been v. Knie- 
riem,* who experimented upon rabbits. In a preliminary experl- 
ment the addition of prepared “crude fiber” to a basal fiber-free 
ration in which the necessary bulk was obtained by the use of horn- 
dust t gave the following results for the urinary nitrogen per day:. 
J. Without fiber... ......... .. 0.9034 grams 
II. With 9.284 grams fiber. .... ... 0.7618 “ 
III. Without fiber........ ..-... 0.7560 “ 
The low figure for the third period is ascribed to the effect of 
the crude fiber still remaining in the digestive tract. In a follow- 
ing series, in which respiration experiments were also made, the 
following results per day were obtained for the nitrogen: 
* Zeit. f. Biol., 21, 67. + Shown to have been entirely indigestible. 
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