74 
COTTON-CAKE. 
By inspecting the foregoing table, it will be seen that the 
nature of the constituents forming cotton-cake in all its five 
varieties is the same as those composing our standard of 
comparison—linseed-cake; and as it is upon the peculiar 
functions of these constituents in relation to digestion, assi¬ 
milation, &c., that the feeding values of the cakes depend, 
I may be excused for briefly reminding my readers of their 
leading characters and destination in the animal economy. 
JFater.— Although, as a component of food, water is of 
great value, physiologically considered, yet, looking at the 
question commercially, it is difficult to assign any value to 
it, so that one need only remark that, in purchasing feeding- 
cakes, all other things being equal, the less water a cake 
contains the higher will be its worth. 
'Flesh-formers. —These components are similar in chemical 
composition and properties to albumen, so that they have 
been termed the albuminous constituents; and from their 
containing the element nitrogen, they have likewise received 
the appellation of nitrogenous constituents. These are the 
materials of food which are chiefly concerned in contributing 
to the formation of the muscle or flesh of an animal, and to 
its other nitrogenized solids and fluids. 
The respiratory constituents (heat-producers and fat-formers) 
contain no nitrogen, and so are often called the non-nitro- 
genized constituents of food. They include the oil, mucilage 
or gum, digestible cellular tissue, and similar bodies. These 
materials furnish the principal quantities of the hydro- 
carbonous matter which, during respiration, undergoes oxida¬ 
tion, evolving that heat which is so essential to the perform¬ 
ance of the vital functions of an animal. If an animal undergo 
but little exertion, or take but a small amount of exercise, 
then a small proportion only of the respiratory ingredients 
of its food suffers conversion into carbonic acid and water, 
and the remainder is stored up by the animal as fat. 
The indigestible fibre , although having the same chemical 
composition as the respiratory constituents, is, as its name 
implies, incapable of undergoing digestion, and cannot, there¬ 
fore, possess a direct value as an article or component of 
food. However, indirectly it is said to do good service in 
giving that bulk to the food which appears so desirable in 
some animals, and of acting as a mechanical stimulant. In 
some cases, as we shall presently see, the physical condition 
of the indigestible fibre may be such as to warrant our look¬ 
ing upon it with suspicion, that is, as a material extremely 
likely to cause injurious effects to follow its introduction 
into the alimentary canal. 
