226 ON THE VARIETIES OF VEGETABLE FOOD. 
nitrogenous principle, will be able to do a larger amount of work 
than if he confines himself to the bread. I am persuaded that 
there is not a dearer food to be found than potatoes, if used alone. 
It is well known that in the case of parties who feed on potatoes 
alone, a large proportion of the starchy granules passes through 
the svstem untouched. So far as subsistence is concerned these 
4/ 
granules are lost, and form part of the excrements. You see, 
therefore, that in mixing food, it is a point of great importance 
to take care not to give too much of one kind of food or too much 
of another. In like manner, too large an amount of the flesh-pro¬ 
ducing principle will be too expensive; on the one hand it will not 
be the best for the animal; on the other hand, it will be extrava¬ 
gant. I don’t know what amount of oil-cake is given by gentlemen 
in this part of the country, but I am persuaded that in many cases 
the amount given to animals is far beyond their requirements, 
and that a considerable portion of it passes through the animal 
unacted upon, a portion only having been made use of for the 
purposes of animal economy, and the rest having been applied 
to the mere purpose of manuring. It is a most expensive 
article thus to make use of. I have analysed varieties of oil¬ 
cake from London, Liverpool, and Marseilles, and, having dis¬ 
covered what amount of nitrogen and bone earth they contained, 
I have then compared them with Peruvian guano. Estimating 
that Peruvian guano contains 16 per cent, of ammonia, I found 
that one ton of it will give 2^ times as much ammonia, and 6 
times as much bone earth as one ton of oil or rape-cake. No 
one who knows the relative price of these things in the market 
will spend his money on oil-cake for the mere purpose of manur¬ 
ing, but will take care that in its use he sees some profit attached 
to the animals consuming it. 
* * * * 
The cooking of food can under no possible condition add any 
thing to nutriment. Those who expect that by cooking food they 
will add to it any thing at all in the shape of nutrition are greatly 
mistaken. All we can do by cooking food, or by any pre¬ 
paration of food for animals, is to assist the animal in applying 
it to its own use. 
# * * * 
With respect to animals which chew the cud, it is necessarv 
that there should be a proper amount of solid matter. I have 
known parties neglect this, and the effect of doing so must be 
injurious. Unless there is a sufficient amount of chopped straw 
or some similar material eaten by cattle fed with such succulent 
food as turnips or mangold-wurtzel, it is impossible for the work¬ 
ing of the animal economy to be properly carried out. 
