8 PRINCIPLES OF ANIMAL NUTRITION. 
their subsequent cleavage in the metabolism of the plant. They 
are chiefly soluble, crystalline bodies. The most common of them 
is asparagin, which has been, to a certain extent, regarded as 
typical of the group. 
The non-proteids are commonly determined by determining as 
accurately as possible the non-proteid nitrogen and multiplying the 
latter by the factor 6.25. In the case of asparagin, however, which 
contains 21.2 per cent. of nitrogen, the proper factor obviously 
should be 4.7, while the factor would vary for the different forms of 
non-proteids which have been observed in plants. It is no simple 
matter, therefore, either to determine directly the amount of non- 
proteids or to decide upon the proper nitrogen factor in any partic- 
ular case. For the present, however, the factor 4.7 would seem 
to be at least a closer approximation to the truth than 6.25. ° 
In the animal body the group of non-proteids is represented by 
the so-called “extractives” or “flesh bases’’ of the muscle, chiefly 
creatin and creatinin. 
Fats.—The fats of the plant, like those of the animal, consist 
chiefly of glycerin compounds of the so-called “fatty acids,” or of 
similar bodies. These are accompanied in the plant, however, by 
other materials—wax, chlorophyl, ete.—which are extracted along 
with the fat by the common method of determination and consti- 
tute part of the “crude fat” or “ether-extract.” The results, 
therefore, which have been obtained in feeding experiments with’ 
pure fats cannot be used with safety as a basis for estimating the 
nutritive value of the so-called “fat” of feeding-stuffs, particularly 
in the case of coarse fodders. 
CarBouyDRATES.— The well-characterized group of carbo- 
hydrates makes up a large proportion of the organic matter of our 
more common feeding-stuffs. This group of substances may be sub- 
divided on the basis of molecular structure into hexosans and their 
derivatives (hexoses, bioses, trioses, etc.), on the one hand, whose 
molecules contain six atoms of carbon or a multiple of that number, 
and the pentosans and pentoses, or five-carbon series, on the other. 
In the grains and other common concentrated feeding-stuffs, and 
particularly in the food of man, the hexose group largely predomi- 
nates, including starch, dexfrin, the common sugars, and more or 
less cellulose. In the coarse fodders consumed by our domestic 
