A PRIZE ESSAY. 
29 
while I walk into a new department of your chemistry. 
You may not understand the reasons of this difference 
in manures—why, for instance, fattening cattle give 
stronger manure than working oxen—without going a 
little into tha mode how animals are nourished. The 
whole may be stated in plain terms thus: All food 
serves two purposes. The first is to keep up the ani¬ 
mal heat, and this part of food disappears in breathing 
or in forming fat; that is, after serving its purpose in 
the animal body, it goes off in the breath or sweat, or 
it forms fat. It is so essential to the action of breath¬ 
ing, that we will term it food for breathing, or the 
breathers. The second purpose answered by food is, 
to build up, sustain, and renew the waste of the body. 
Now all this is done from the blood. To form 
blood, animals must be supplied with its materials 
ready formed. They are ready formed in plants; 
and animals never do form the materials for making 
blood. We may, therefore, term this kind of food the 
blood formers. We have, then, two classes of food; 
the breathers and the fat formers, and the blood 
formers. If we look to the nature of these different 
classes, we find that sugar, starch, and gum are 
breathers. Now there are three principles found in 
plants, exactly and identically the same in chemical 
composition with white of egg, flesh, and curd of 
milk. Now these three principles, exactly alike, 
whether derived from animals or from plants, are the 
only blood formers. I shall not, reader, tax your at¬ 
tention further upon this subject, than to say and to 
beg you to remember these important facts: First, 
all food for breathing and forming fat contains only 
these three elements, oxygen, hydrogen, and carbon. 
Secondly, all food for forming flesh and blood, in ad¬ 
dition to these, contains nitrogen. 
This is the gist of the whole matter, so far as relates 
to manure. Bear in mind, as you go on with me, 
reader, this fact, that of all the food animals take, that 
alone which can form flesh and blood contains nitro- 
