THE FOOD. 9 
herbivorous animals, while the hexose group is also largely repre- 
sented it is accompanied by no inconsiderable quantities of carbo- 
hydrates belonging to the pentose group. The individual members 
of this latter group are both less abundant and less well known 
chemically than the hexoses, and at present our knowledge of their 
actual nutritive value is somewhat scanty. Since the methods for 
their determination are based upon the fact that they yield furfural 
upon boiling with dilute hydrochloric acid, some recent analysts 
have proposed the term “furfuroids” as a more appropriate desig- 
nation of these substances as determined by present methods. 
In the conventional scheme for the analysis of feeding-stuffs, the 
carbohydrates are subdivided, not upon the basis of their chemical 
structure but upon the basis of their solubility. “Those members 
of the group which can be brought into solution by boiling dilute 
acids and alkalies under certain conventional conditions are grouped 
together as “Nitrogen-free extract,’ while those ingredients 
which resist solution under these conditions are designated as 
“Crude fiber.” The more common hexose carbohydrates, such as 
starch, sugars, etc., are included in the nitrogen-free extract, while 
the larger part, although not all, of the cellulose is included under 
the crude fiber. At the same time, more or less of the pentose carbo- 
hydrates or “furfuroids” are found in both these groups, while the 
crude fiber of coarse fodders contains also a variety of other ill- 
known compounds, somewhat roughly grouped together under the 
general designation of ligneous material. 
Digestibility.—A part of nearly all common food materials is 
incapable of digestion and is rejected in the feces. In the food of 
man and that of carnivorous animals this indigestible portion is 
usually small and may disappear entirely. In the food of herbivora, 
on the other hand, there are contained relatively large amounts of 
substances which are incapable of solution in the digestive tract, 
while varying proportions of materials which in themselves are 
capable of being digested may escape actual digestion under some 
circumstances. In the latter animals, therefore, it becomes par- 
ticulary important to determine the digestible portion of the food. 
The digestibility of a feeding-stuff is estimated indirectly by deter- 
‘mining as accurately as possible the undigested matter eliminated 
from the body in the feces and subtracting it from the total amount 
Digitized by Microsoft® 
