90 MANUFACTURED FOODS FOR AGRICULTURAL STOCK. 
natural constituents existing in his soil , and the residue from 
previous manures and crops. The application of a small quan¬ 
tity of ammonia and mineral matter will often yield as great 
an increase of vegetable produce, as if twenty or thirty times 
the weight of farm-yard dung had been employed. This is 
not to be wondered at, when it is considered that by far the 
greater bulk of the dung consists of water and other con¬ 
stituents which the plant can obtain either from the air or 
the soil. We thus get, by the use of concentrated manures, 
a much greater weight of increased produce than there was 
of manure employed. The case is very different in the 
supply of food to our stock. The quantity of the con¬ 
stituents returned in the solid and liquid excrements, and in 
the increase of the animal, must invariably be very much 
less than was contained in the food consumed. No concen¬ 
tration of constituents, nor any amount of supply of some 
only, of those required for the respiration , the perspiration, 
the excrements , and the increase , can enable the animal to 
obtain a particle of what is requisite for these from any other 
source than his food. 
In the case of stock-foods, therefore, the scope for econo¬ 
mical manufacture or concentration is very limited. Among 
the natural complex foods, hay may be said to be more 
concentrated than straw, and corn more concentrated than 
hay. Of the individual non-nitrogenous, or so-called respi¬ 
ratory and fat-forming constituents of food, fatty matter is 
very much more concentrated than starch or sugar. But 
our ruminant animals cannot thrive upon exclusively con¬ 
centrated food, even though it be so in the limited degree in 
which it exists in corn. They require a certain amount of 
the bulky but innutritious woody fibre, which they find 
already combined with other constituents in hay or straw. 
Those animals, such as pigs, w hich do not require the same 
proportion of woody fibre for their digestive operations, are 
provided wfith a suitable combination of starch, sugar, oil, 
nitrogenous substance, and mineral matters—already formed 
in corn and other natural foods—far more economically than 
they could be supplied with them by the intervention of 
manufacturing processes. 
There is, in fact, only one manufactured staple article of 
food employed by the farmer with advantage on the large 
scale. This is oilcake. Even oilcake is not manufactured 
exclusively for the purpose of feeding ! it is the residue of 
a process for obtaining oil, the value of which, to a great 
extent, meets the cost of the production of the cake. The 
cake w T as produced before there was any demand for it as 
