What does the solid dung contain? Liquid manure? The breath?
If any of the food taken up by the blood is not returned as above stated, it goes to form fat, muscle, hair, bones, or some other part of the animal, and as he is not growing (not increasing in weight) an equivalent amount of the body of the animal goes to the manure to take the place of the part retained.[V]
We now have our subject in a form to be readily understood. We learn that when food is given to animals it is not put out of existence, but is merely changed in form; and that in the impurities of the breath, we have a large portion of those parts of the food which plants obtain from air and from water; while the solid and liquid excrements contain all that was taken by the plants from the soil and manures.
The Solid Dung contains the undigested parts of the food, the insoluble parts of the ash, and the nitrogenous matters which have escaped from the digestive organs.
"Liquid Manure" the nitrogenous or second class of proximates of the digested food, and the soluble parts of the ash.
The Breath contains the first class of proximates, those which contain carbon, hydrogen and oxygen, but no nitrogen.[W]
FOOTNOTES:
[V] This account of digestion is not, perhaps, strictly accurate in a physiological point of view, but it is sufficiently so to give an elementary understanding of the character of excrements as manures.
[W] The excrements of animals contain more or less of sulphur, and sometimes small quantities of phosphorus.