112 PRINCIPLES OF ANIMAL NUTRITION. 
Kaufmann likewise interprets the results of the respiration ex- 
periments cited in another connection on p. 99 as demonstrating 
the production of fat from proteids, but in view of the brevity of 
the experiments (five hours), and the fact that they covered the 
period of most active nitrogen cleavage, this conclusion seems 
hardly justified. 
Cremer * has reported the results of an experiment upon a cat 
which he regards as showing a formation of fat from proteids. The 
animal, weighing 3.7 kgs., passed eight days continuously in the 
respiration apparatus and received per day 450 grams of lean 
meat. No complete nitrogen and carbon balance is reported. The 
average daily excretion of nitrogen was 13 grams. Assuming the 
ratio of nitrogen to carbon in fat and glycogen-free flesh to be 1:3.2, 
this corresponds to 41.6 grams of carbon in the form of proteids, 
while the total excretion of this element was only 34.3 grams, thus 
showing a retention by the organism of 7.3 grams per day. The 
body of the animal at the close of the experiment was found to con- 
tain not more than 35 grams of glycogen and sugar, while the ob- 
served gain of carbon during the eight days was equivalent to 
about 130 grams of glycogen. It is therefore concluded that fat 
was formed from proteids. In three other experiments, with an 
abundant meat diet, it is computed that from 12.6 to 17.0 per cent. 
of the carbon of the metabolized proteids was stored in the body. 
Gruber { has recently reported two experiments, dating from 
the year 1882, in which a dog was fed 1500 grams per day of lean 
meat. The nitrogen of feces and urine were determined daily 
for six and eight days respectively and the carbon dioxide of the 
respiration on five days in each experiment; the carbon of urine 
and feces and of the metabolized proteids was computed from the 
nitrogen, using for the carbon of the proteids the factor 3.28. The 
excretion of nitrogen approximately equaled the supply, especially 
on the Jater days of the experiments, but from 10 to 15 per cent. 
of the carbon was unaccounted for in the excreta. The total reten- 
tion of carbon during the experiments, together with the equivalent 
quantities of glycogen, were: 
* Jahresb. Agr. Chem., 40, 538; Zeit. f. Biol., 38, 309. 
{ Kohler (Zeit. f. physiol. Chem., 81, 479) found an average of 1:3.16 for 
the fat-free flesh of cattle, swine, sheep, rabbits, and hens. See p. 64. 
Zeit f Biol., 42, 409. 
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