THE RELATIONS OF METABOLISM TO FOOD-SUPPLY. 113 
Carbon. Equivalent Glycogen. 
Experiment 1, seven days..:..... 113.9 Grms. 256.3 Grms. 
ie 2,eight “ ........ 195.9 “ 441.0 “ 
These amounts of glycogen are much greater than have ever 
been found in the body of a dog of this weight (about 20 kgs.), and 
the larger part of the storage of carbon must therefore have been 
in the form of fat. 
In addition to the above results on normal animals, Polimanti * 
has reported experiments apparently, showing a formation of fat 
from proteids in phosphorous poisoning. The latter investigation, 
as well as those of Cremer and of E. Voit, have been the subjects of 
searching criticism by Pfliiger,t who claims to have shown the in- 
sufficiency of the experimental evidence adduced, but it is impos- 
sible here to enter into the details of these controversial articles. 
Negative results have also been reported by Kumagawa & 
Kaneda,t Rosenfelt,§ Taylor,|| Athanasiu,{{ and Lindemann,** but 
in a matter of this sort negative evidence naturally carries much 
less weight than positive, and on the whole there would appear 
to be good reason for still regarding the proteids as a possible 
source of fat. 
DirFicutty oF PRroor.—A serious difficulty in the way of an 
unquestionable demonstration of this possibility lies in the limited 
amount of proteids which an animal can consume. As we have 
seen, a relatively large supply of them is necessary even to produce 
nitrogen equilibrium, and a still further large addition is required to 
supply the demands of the organism for energy. Only the proteids 
supplied in excess of this latter amount are available for fat produc- 
tion, and thus it comes about that the limit of consumption and 
digestion by the animal is reached before any very large produc- 
tion of fat can take place. 
On the other hand, if non-nitrogenous nutrients (carbohydrates 
* Arch. ges. Physiol., 70, 349. : 
} Ibid., 68, 176; 71, 318. 
£U. 8S. Dept. Agr., Expt. Station Record, 8, 71. 
§ Jahresb. Physiol., 6, 260. 
|| Ibid.. 8, 249, Jour Exper. Medicine, 4, 399. 
q Arch. ges. Physiol., 74, 511. 
** Zeit. f. Biol., 39, 1. 
